I was a big MST3K fan, but due to a lack of funds, haven't tried either one yet.
I'm hesitant to try Rifftrax because the synch thing sounds complicated. There are chimps who are more computer savvy than I am. But I know Rifftrax has some non synch DVDs out.
I'm leaning toward Cinematic Titanic because all of their material is on DVD, but part of me wants to see say-Twilight MST-ied, because I'm afraid to watch it un-MST-ied.
Any fans who've tried it and are fans of one, both or neither out there?