On the ground, the Engineer is tough to beat. However, in space I couldn't care less for the Engineering class. Of the three, they have the fewest offensive (read: zero) and are only designed to keep themselves alive. Sci, on the other hand, comes with some excellent debuffs and can slot some good team heals. The one thing an Engineer can do better than anyone else is tank, which is an amazing help, but since this game's aggro system is so wonky, they rarely tank at all.

In an ESTF with nothing but skilled players, the Engineer will be sitting there living it up and doing the least amount of anything. Meanwhile, a Tact is holding aggro and tearing into the bad guys, while a Sci is debuffing the bad guys and keeping the tact alive long enough to kill them. Honestly, until Engineers can figure out how to tank properly, they might as well stay at the space dock. A team of Tacts with a couple Science officers is all you need.

By the way, the answer is Science. Such a fun class.