Good evening,
I'm currently using the XII MACO deflector/shield and the good ol' Borg engines.
Considering that at least 2 months are needed until Omega T5 I'd like to know which engines
I should use until then. (I'm sure there are many players are in a similar situation.)
I tend to use 25 engine power (after skills etc I still get ~48, though).
I heard that Jem Hadar and Fleet Engines with the right mods are pretty good.
Any help would be appreciated

Aegis Engine.

That is all.

The Efficient Impulse Engine you get from a mission, can't remember which one, can do very well if you don't feel like spending anything.

http://www.stowiki.org/Efficient_Impulse_Engines

Lazy bum -.-

Anyways, I agree, that engine or the Assimilated Subtranswarp Engine. AKA retro Borg Engine (if you already have one, if not, oh wells).

Aegis engine seems like a very solid choice, I'd really like to know how the additional 5% defense are calculated.
The wiki says the Efficient Impulse Engine was nerfed quite a bit, the power bonus in the preview window was very low at least. Turning and speed are a bit worse than the other endgame engines, too.
I'm currently trying the JH engines and they're pretty good. Only disadvantage is that they're combat engines which kinda sucks in the new Tholian STFs where I think you can save quite a bit of time with Hyper Impulse engines. At least you get +5 weapon power when flying at full speed settings x)

the aegis has a flat 5% def bonus
the efficent engine works similar to the KHG engine power level stats. Whatever is your max stat that power gain will be 0...whereever you are below a certain powerlevel (i usually get the full bonus in engine and shields) you get the full 3.8 power.
still, stand alone, the KHG would be my choice. the restart is amazing.