My current take on engines:
- Engines are the most important component of any useful fighter.
- Engines are very important in specific frigate setups, especially zerg swarms.
- Engines are somewhere between almost useless to actually hurting the fleet in cruisers.
Allow me elaborate on that last point…
First of all, the obvious. Spending more money on engines means you have less money to spend on very useful things like weapons, shields and armor.
Secondly, a very important aspect to building a good fleet is positioning. Optimally all cruisers should come into weapons range at the exact same time, spreading enemy attacks to several of your ships, and concentrating fire on the enemy to quickly destroy their ships. Faster engines don’t help the formation of your fleet, and in many cases they cause it to go into disarray.
Not getting to the enemy fleet in time with slow (or stationary) cruisers is usually not a problem. With a lot of fighters the enemy can slowly whittle your armor away, but there are much more effective countermeasures to this than engines. The “kiting” tactic mentioned earlier - staying out of enemy weapons range but within your long range missiles - would work, except even the largest maps are too small, your fleet would get cornered and destroyed.
There simply isn’t enough benefit to cruisers with fast engines right now.