Having recently watched both Gravity and 12 Years a Slave, I can say without a doubt that Steve McQueen's 12 Years A Slave was not only the winner, but the easy winner. Of course, having nothing to do with the few amusing or laughable theories I've seen around such as "White Guilt" or "Anti-Sci-Fi Bias."
12 Years a Slave has an actual script, strong narrative and some swell performances to go along with great cinematography. Gravity is a well-directed audiovisual treat, not many attempt to take that from it, but overall it's simply an above-average film experience. When the most notable performance in a film is Sandra Bullock heavily panting constantly (in an oddly erotic tone, if I'm being facetious as when I was viewing that entire 45 minutes of it in the film), there's not much weight to be given there. I blame the script more than wonderful Sandra for this incident, but that's how it goes.
As for the music, Steven Price's original score worked very much to Gravity's favor and was one of its stronger elements by far. Price winning the Oscar for that score is fine. I wasn't overwhelmingly on its side, but it certainly was composed intelligently.
In short, Gravity rightfully obtained about all the 2014 Oscars under its belt, but it didn't deserve Best Picture over 12 Years a Slave on overall merit. Thankfully, and perhaps not surprisingly, that worked itself out in the end. The best picture, 12 Years a Slave, won Best Picture last night.