I like both of those universes but I have to say that I preffer Star Wars. It seems to be "better" constructed because Warhammer 40k lets face it is background for a tabletop game, there is no real focus on anything (ok there is a lot of focus on space smurfs
) there is like dozen of different factions which don't exactly fit with each other. To name few there are Tau which have "japanese mecha" design to them and are polite and friendly communists who just want to get along (ok not really), there are Necrons which are Arnie inspired highly advanced technologicaly ancient robots who just want to destroy everything and are threat to whole known universe (like aparently every other species, its done this way so players of one faction won't be "losers" in fluff so people can argue on internet forums which race will rule over galaxy), we have daemons and forces of chaos which are eeevil counterpart of "main player" - Imperum of Man. I won't go in detail about different factions inside imperium because its not the point. The empire is on neverending brink of destruction (its not a story but GAME so they can't exactly have one faction win over another, whole universe is in status quo) since their beloved Emprah died and now people worship his corpse sitting on a throne. So even with more recent Star Wars movies (episodes from 1 to 3) which are utter cr*p Star Wars wins because it has some plot running, its not just a background for something else.Ps. "I've got a bad feeling about this". Vs threads tend to end in flamewars.