Naval Game System Comparisons
In a nutshell, there are four separate Minden game systems that cover tactical naval combat.  Each system is different; no particular system is compatible with either of the others.  These game systems are:  SALVO!, BATTLESHIP CAPTAINDREADNOUGHTS & BATTLECRUISERS, and NAVTAC.  

We will briefly compare and contrast these four systems, not each particular game or edition within the system.  This means that if a particular product is said to belong to a particular system, the game will play like others in that same system.  For instance, Battle of the River Plate belongs to the BATTLESHIP CAPTAIN system, as does Tsushima 1905, Action Stations, and Battleship Captain 3rd ed.  This means that each of these games uses the BATTLESHIP CAPTAIN game system (though there may be some special rules included to reflect a particular era or emphasis).  But it means that none of these games is compatible with any game in the SALVO! series, or the DREADNOUGHTS & BATTLECRUISERS series, for instance.

The following explanations are meant to provide enough information for players to determine which game system they prefer, or whether they want to purchase a particular game they may not be familiar with.  The explanations are not exhaustive, but are meant to be helpful.
SALVO! GAME SYSTEM

The Salvo! game system was designed for solitaire play.  While possible to play with two players (and can be fun doing so), solitaire was the design intent, not an after thought, for the game system.  Salvo! games typically involve a small number of ships, with scenarios playable in just a few minutes.  You need three six-sided dice to play.  It is probably the most simple of our naval game systems.

Warships are rated in a variety of categories.  (See Ship Counter Key from Great War Salvo! to the right, for example.)  Movement is relative, by "range bands" (e.g. Short, Medium, Medium Long, etc.), and kept track of on a piece of paper or game log.  This is not a miniatures game system; you do not need to use physical ship counters (just have their ratings handy).  This means the game can be played with a very small footprint, even on a airline tray table.  

While there are some differences between WW1 and WW2 Salvo! games (to take into account the nature of each war, and the weaponry involved), the game system and tables are very similar.  You control your side, and the game system controls the opposition.  Movement is simple, usually just a choice between "Close" (your bow guns bear, and your close the range with the enemy), "Offer Broadside" (your broadside guns bear, with no range change), and "Withdraw" (your stern guns bear, and relative range increases).   Combat is resolved on a Fire Table, to determine if you straddle the enemy or miss.  If you straddle them, you roll 3d6 and total on the Straddle Table.  This gives a wide range of results, sometimes prompting you to roll on another table to find the final result.  Hits can be T (Turret) hits affecting guns, fire direction, and thus firepower, S (Speed) hits to engineering, propulsion, or bridge damage, affecting speed, and F (Flotation) hits from explosions, flooding, or structural damage.  A ship is sunk when it has received more F hits than its Flotation rating.

Optional rules vary according to game and era, but include such things as torpedoes, weather, crew quality, ammunition expediture, and many more.  The game system represents combat between surface ships, and does not cover aircraft or submarines.
BATTLESHIP CAPTAIN GAME SYSTEM

The Battleship Captain game system is a miniatures game designed for two (or more) players.  While possible to play solo, there are no rules to govern solitaire play.  Battleship Captain games are probably the most involved among the Minden naval games.  It is designed for high playability, but the sequence of play is more involved than any of the other game series.  Small or large naval engagements (e.g. Jutland) are possible and easily set up.  The game scale is six turns per hour, with one inch distance on the table (or floor) representing 500 yards.  Ship counters are rendered at approx. 1/4500 scale.  (Though you may easily play with other scales.)    The system has games that cover the Pre-Dreadnought, WW1, and WW2 eras. You need two six-sided dice to play.

Warships are rated in a variety of categories.  (See Ship Counter Key from Battle of the River Plate to the right, for example.)  Movement is facilitated by a ruler or tape measure as counters are moved on the playing surface.  The system's Sequence of Play is:  Movement phase 1, Combat phase 1, Movement phase 2, Combat phase 2.  Ships (or squadrons) move up to half their current speed in each Movement phase, from slowest ship (squadron) moving first, and fastest moving last.  Ships may typically fire their guns in one (not both) of the Combat phases.  Gun ranges depend on the size of the gun, and environmental factors.  Submarine and aircraft combat is not simulated in this system; it covers surface engagements only.
Fire combat is odds-based (firepower compared to defender's armor rating).  Fire factors increase at shorter ranges, and decrease at longer ranges.   The Fire Combat Table will determine if a Hit occurs.  If so, you roll on the Hit Table to see if damage occurs.  Possible damage results include T damage (turrent or fire control), F damage (flotation), S damage (superstructure), and D damage (deck).  In addition, three special type of damage may occur, if/when you are directed to roll on the Critical Hit Table, the Plunging Fire Table, the Special Damage Table, or the Internal Damage Table.  There is a wide range of possible damage effects from these tables. There is also the possibility of accumulated damage occuring, e.g. for every three S hits a ship takes, it receives an extra T hit.

A ship is Dead in the Water when it has received as many F hits as its Flotation rating.  Once DiW, a ship runs the risk of sinking if it takes subequent hits,  Further, if a ship receives--in a single combat phase-- F hits more than half of its Flotation rating, it sinks due to its damage control being overwhelmed. 

The game system has many advanced rules and options such as weather, changing visability, torpedoes, Narative Damage tables, Night combat, Ammunition rules, era-specific rules, and many others. 
DREADNOUGHTS & BATTLECEUISERS GAME SYSTEM

The Dreadnoughts & Battlecruisers  game system is a miniatures game designed for two (or more) players.  It does include a Solitaire module that allows for solo play, using modified rules but the same ship counters.  The game covers World War I naval combat between surface ships (no submarine rules are provided).  While the ship counters resemble those of the Battleship Captain series, the game system itself is completely different.  D&B is slightly less involved than BC, and may therefore be considered slightly higher in playability.  The trade off is that combat and movement are less nuanced.  Like BC, small or large naval engagements (e.g. Jutland) are possible and easily set up.  Again, like BC, the game scale is six turns per hour, but with one inch distance on the table (or floor) representing 1000 yards.  Ship counters in the current D&B games are rendered at 1/3000 scale, so larger than the ships in BC series.  (Though you may easily play with other scales.)    You need two six-sided dice to play.

Warships are rated in a variety of categories.  (See Ship Counter Key from D&B: High Seas Deluxe Ed. to the right, for example.)  Movement is facilitated by a ruler or tape measure as counters are moved on the playing surface.  The system's Sequence of Play is:  Movement phase, Combat phase.  Ships (or squadrons) move their current speed in the Movement phase, from slowest ship (squadron) moving first, and fastest moving last.  Ships may fire their guns in the Combat phases if enemy ship is within range.  Gun ranges depend on the size of the gun, and environmental factors. 
Combat resolution is less invoved than BC.  Combat starts by comparing firing factors vs defending armor rating, and rounding down to nearest odds (like 1-1, or 2-1), followed by the roll 1d6.  This determines if a Hit occurs.  If so, you roll on the Critical Hit Table, to see if damage occurs.  F hits will degrade the ship's firepower, and M hits its movement.  It is possible that a ship can be sunk (given the right modifiers) outright.  Otherwise, a ship is sunk if it has more M hits than its Flotation rating.  Other types of damage can occur from the Performance Table and the Special Damage Table.  Essentially, for each F hit a ship receives, its firepower ratings are lowered by 25% (this is in the standard game; in the advanced game Advanced Fire Progression ratings are used, and ships (depending on rating) can lose less or more percentage of its firepower, per F hit.  

There are tons of optional rules covering all sorts of things, from weather, changing visibility, torpedoes, incremental odds, ammunition expenditure, flagships, flash vulnerability, immune zone modifiers, repairs, Narrative Damage Tables, merchants and armed merchant cruisers, national navy characteristics (affecting crew, command control, repairs), and more.

Overall, D&B is probably an easier system to play and master compared to BC, with BC having more nuance.  So, overall the games are similar in what they simulate, they just approach the simulating in different ways.
NAVTAC GAME SYSTEM

The NavTac (Naval Tactical) game system is a miniatures game designed for two (or more) players. It uses the classic Fletcher Pratt naval system, but substitutes rolling two dice to resilve combat rather than range estimation.  Otherwise, it is basically very similar to FP.  The game covers World War I naval combat between surface ships (no submarine rules are provided).  The game scale is five turns per hour, with one inch distance on the table (or floor) representing 500 yards.  Ship counters are rendered at 1/3000 scale, but you can use any scale you wish.  You need two six-sided dice to play.

Warships are rated in a variety of categories.  (See Ship Counter Key from NavTac: Coronel & Falklands to the right, for example.)  Movement is facilitated by a ruler or tape measure as counters are maneuvered in the usual manner on the playing surface.  The system's Sequence of Play is:  Movement phase, Combat phase.  Each hit a ship takes will give it damage points.  Accumulated damage points will lessen the ships firepower and movement ability.  How much damage a hit gives depends on the size of the shell, and how much damage before firepower/speed is affected depends on the defending ship's displacement.  There are many optional rules you may esily incorporate into play, depending on your preferences.

The NavTac series will appeal to traditional naval game players, especially those familiar with FP, or to naval gamers looking for a change of pace.