I don't use too many of the social networking sites out there, but I'll admit to still using facebook. I have a twitter account, but I don't really use it much...I'm the talkative type despite my natural shyness and hermit-like nature...I can't type my thoughts in a short sentence. So for me, facebook is better between the two- though it can be frustrating. I get tired easily of the game requests, and some of my friends tend to post randomly depressing things, but some of them are also very upbeat and I find facebook helps me keep an eye on some things that are hard to otherwise. It has its ups and downs, but overall I like it. Though I think facebook is narcissistic since it has it's own page you can like...about itself o.O;
I also have a google plus account just mostly because I have gmail. My only friends on it are my dad and my uncle, who occasionally messages me on it, but otherwise it is completely silent. I probably have my old myspace somewhere, but I haven't really used it since it was popular when I was in like...sixth grade, which was at least eight years ago, considering I was twelve and I'm almost 21 now. Oh, and I'm not sure what Tumblr is considered, but if it's social networking, I use it mostly to stalk tags based on my favorite anime and video games and such. And my friend who posts random art on it sometimes.