Not in Dark Avatar... Dread Lords let ships stockpile engines cheaply, but Dark Avatar doesn't... an engine can take up a huge portion of your ship. Heck, most warships won't have an engine at all until late game! This makes the speed race ability as well as the engine tech bonuses very importance. A warship (minus engines) of a race with impulse drive researched will move at 2 pc/week. The same warship in the hands of a race with warp drive researched move's at 3.
Also, to answer the original question, Dark Avatar also allows speed to have a MASSIVE tactical advantage, given the first strike ability (Arceans, though custom races can also have it). With that ability, you can wipe out entire fleets without receiving return fire... but only if you make the first hit. If your speed is equal to your opponents, you're stuck waiting for them to move if you want to make first strike. If it's lesser, then you have to fly really defensively in order to lure enemy ships close enough. If it's greater though, you can get first strike almost every time. Needless to say, when first strike abilities are involved, ship speed is KING.