Fair enough!
However, my question to the SFB/FC players is this: what, if not "total power", is the determining factor for you when evaluating how "fast" a ship is?
In SFB/FC all ships have a 'move cost', how much energy they pay to move one hex on the game board. This is determined by various factors, but is *not* directly related to the number of boxes on the ship diagram.
It is probably best to think of each system box as 'the capability to do something' rather than an actual physical piece of machinery - a much more vague relationship than in Starmada!
The ship's top speed in the game is (in FC) the number of power-generating boxes divided by the move cost. On the other hand in SFB, only the warp engine boxes can move the ship (plus a flat one hex per turn from one impulse engine box). As a result, ships tend to be a bit faster in FC. There is an in-game speed limit of 31 hexes per turn in SFB, and 32 in FC.
So for an undamaged Klingon D6 (or it's Romulan KR equivalent) their top speed in SFB would be (30 warp boxes) divided by the ship's move cost (1), plus one point of impulse power, for 31.
A War Eagle only has 20 warp boxes, but also has a move cost of 1, so goes at 21 flat out, including impulse power.
During a game, the ships will seldom move at anything like that speed, as power has to be diverted to weapons, shields, tractor beams, transporters, electronic warfare et.c et.c.
The 'Fast' cruisers mostly (IIRC) have 36 warp/move cost 1. While they still can't exceed speed 31 in an SFB game, in practise they do run at a higher operating speed, as they have more power in total, and fewer weapons to *use* that power.
In FC, non-warp boxes can be used for movement, giving the War Eagle a top baseline speed of 24 with a couple of hexes of accelleration during the turn giving an effective speed of 26, leaving no power at all for weapons, cloak, et.c.
In contrast, a D6/KR could set baseline speed 24, accellerate every impulse for an effective speed of 32, and still have five points of power left over to pop off a few phaser shots or whatever. (That's ignoring any energy in batteries at the start of the turn).
Hope that clarifies it. Apologies for being so long winded.