Hmm, where do we start? I suppose I better start by taking the ST is better stance, since this is a Star Wars website ST is bound to be under represented.
Star Trek is cool because it represents a functioning Utopian society where everyone works their butts off to improve mankind and so on. It is even cooler that all these people whether they are high ranking crew members of a Starship or the looser who cleans the sonic toilets, they are all getting paid nothing and yet they are still incredible proud of their careers. How many times in Star Trek has somebody told one of the Captians, "Capt., if you do this then you can kiss your precious career at Star Fleet goodbye."? A variation of that line could almost be found at least once in every season of each of the various ST series. You have got to love that kind of dedication these guys have! You have also got to love how lax Star Fleet is on their regulations. How many times can a Star Fleet officer say, "to hell with their orders" and get away with it? I think if we are ever to find the answer to that we are going to need a ST series to last a LOT longer than just eight years.
These things make ST great. Star Wars is too realistic. An Imperial Officer messes up just once he gets Force strangled to death. No Imperial Officer has EVER said anything along the lines of "to hell with their orders", he is to worried about carrying out every single order to 100% perfection to avoid sudden death to be considering the possibility of thinking about maybe even letting the idea of insurrection or even "skipping a step" of any given order cross his mind.
In Star Trek if you don't want to die, all you have to do is avoid wearing red (And I am not just talking about lousy awayteam members. Does anybody remember what color Spock was wearing when he died? Yup, red). In Star Wars the potential for death awaits you regardless of clothing color. Obi-Wan wore brown, Biggs wore orange, Vader wore black, Yoda wore a sort of off white potato sack, and the Emporer was wearing grayish blue, and they are all dead.
In ST a collective society is unrealistically considered a fantastic thing and a product of evolution, in SW a similar society is considered something worth dying to rebel against.
In ST you can make any number of different aliens by gluing on fake years, antea, pig noses, or monkey ears, everyone looks very much like humans, only different. In Star Wars there are all sorts of creepy looking aliens of all different shapes and sizes, one even looks like an impressive cross between a sock puppet and a chicken. Surely if there were real aliens somewhere in the universe there is bound to be a species that would appear to human eyes to be a cross between a sock puppet and a chicken. The amazing thing is some EU writer actually wrote a love story between the sock puppet chicken alien and the werewolf. As I read this story I was standing beside myself in awe that such tripe would every be published, but to be perfectly honest, I could imagine if there really were erewolf aliens, they might find sock puppet chickens to be very attractive. Realistic or not, I stopped reading all EU after this.
So, my conslusion is that SW is way too realistic. While Star Trek may aim for realism on scientific things, Star Was wins realism for everything else. The peaceful hidden slaughterhouse that is the politics of ST and much more settling and enjoyable to watch than the terrible and brutal reality of SW's Galactic Empire that pratices enthic cleansing, conscription (pre-PT anyway), and brutal means of meeting their desired ends. Sometimes the truth is not what we want to hear. So excuse me as I go stick my head in the sand and watch me some Star Trek.