I played GQ I and then II for twenty years plus. It's the rule set Jim O'Neil started me off with in Germany in the late 70s. The primary difference (and it is huge tactically) is that a ship's defense is based on her tonnage and belt armor as I recall. That plays to the strengths of Japanese heavy cruiser design and completely masks their weaknesses IMHO. That is because the strengths of Japanese design, heavy gun power, good belt armor and about 25 to 35% cheat in treaty weight get full play. However, it completely hides the fact that no Japanese cruiser gun mount has more than 1 inch of armor. It just does not model it. That means that those ten 8 inch guns get treated as if that 3,500 extra tons is devoted to their protection when almost none of it is. GQ3 fixed that by modelling both belt and turret armor. In GQ3, Japanese heavy cruisers act as they did historically in that they are hard to sink and easy to cripple. The Japanese CAs in DTMB are all the best Japanese CA classes (Myoko, Takao & Mogami). Believe me when I say that 6 of those together (and that is very likely in DTMB) is daunting enough IMHO using GQ3. But if you are playing the Allies with a standard start and have opted for GQ 1 or 2 as your tactical rules then you are a better man than I Gunga Din.
WMC