@ogre_h
There’s no single correct answer because the decision involves the following choice: whether you want the size of a given naval sculpt to reflect a particular A&A general unit type or whether you want it to reflect the actual size of a specific warship relative to other specific warships. Each decision involves a trade-off, so it comes down to individual preferences. If you go with the first option, it simplifies play because each unit type can be identified directly from its size, but at the expense of realism. If you go for realism, it means that you need to rely on shape to identify the unit types. For some naval units this is easy: aircraft carriers, submarines and naval transports are impossible to misinterpret because their shape is so distinctive. The problem units are the surface combatants: battleships, cruisers and destroyers. Naval enthusiasts can usually tell the difference without too much trouble, but not everybody is a naval enthusiast. Pointing out, for example, that most A&A destroyer sculpts have transom sterns will cause some people to say “Ah, that’s what I’ll look for!” and others to say, “Huh?”
In case this helps your decision, keep in mind that many of the A&A sculpts which represent a given unit type (naval or otherwise), and which have a uniform set of combat values under the game rules, correspond to real-world hardware that varies wildly in its characteristics. For example, the Soviet battleship sculpt is based on the First World War Gangut class, which in real life would have lasted about five minutes in combat against the Second World War Iowa class on which the US battleship sculpt is based. So even the shapes of the naval sculpts, even if you disregard the size, add up to an overall picture that’s, as you called it, dissonant.