none they both suck ..... but twitter is better because it has live f1 updates yes and twicher has such a low character limit you cant type anything worth saying...
They're both different services. I have the Facebook App, and have Echofon Pro for twitter. And I use both of them quite often throughout the day. The Facebook app lets you do a lot more, because Facebook as a service does more than twitter.
As with any Social platform, it is what you make it, if you try twitter for a couple of days and lurk, follow celebs, you are not going to get much out of twitter, if you converse, follow people with similar interest , and participate, it's a smashing place to hang out. I use Facebook for family and old school friends, and twitter for my interests. ;0)