Enough Space Opera and Pulp to keep things fun and moving for everyone with enough crunch to keep it honest enough to be believable. Not Star Wars, but not 2001: Space Odyssey, either. The scale slides back and forth depending on the needs and tempo of the game session.
I use Asmivo's rule on technology a lot of the time unless more is required: it is enough to say it is a laser pistol or Jump Drive without having to describe it exhaustively because the story's overall believably supports it as common fact and the reader understands what you are talking about because of that. In my game we all understand we are playing a scifi RPG and none of us (usually) are engineers and rocket scientists, and we are all there to have fun and adventure.
So it is usually sufficient to just tell the players they are getting shot at by a 3m long, 2m high orange centauroid dragon-y thing ridden by what can be best imagined as a vicious-looking super otter in fanciful armor and wielding a bell-mouthed thing that cooks you in your combat armor at 100 meters or so. If the players want more crunch they can wait till the aliens get close enough for the drangon-y centauroid to pull out its huge spiky mace to clobber them with.
Me though, oh jeez...as an old school grognard of infamous reputation for nit-pickyness and detail I can spend days worrying some rule process or design like a dog does a bone. There was a dark time once of players moaning, "Oh no, Scotty has new rules....." nearly every week.