We are now on both Twitter and facebook. I dreaded signing up for facebook as I have enough work to do online but you got to go 100% so we took the bait. Twitter has been good to network on Twitter... haven't had a good CTR by using Twitter yet. We will eval Twit and facebook in several months to see our results.
Facebook actually has a higher click through rate, thats because you build more of a personal bond over Facebook, where as on Twitter your generally just using a one way communication system that only sometimes is two way.
u really have to use both and more.. but fbook usually gets more quality interaction then twitter does
It's currently twitter, but wouldn't sleep on facebook! i think facebook will out live twitter in the long term unless twitter comes up with something spectacular.