The tone and subgenre of the game has a big bearing on this issue as well. A tongue-in-cheek space opera allows for more eccentricity than a hardish science fiction game.
I've always been a fan of PCs being a good fit for the type of game that's intended. A game where the PCs are a random bunch of survivors on the last rustbucket out of an exploding space station is going to have a very different feel to one where the PCs are are all created with specific shipboard roles in mind, especially if some sort of formality or discipline applies.
The very same event on paper tends to play out very differently in different subgenres, eg an alien infestation could be tribbles in a comedy episode, or xenomorphs in a horror one.