The Crystal ships both carry around 700-900, I think. I've been on them both and enjoyed them both very much. I think my dh prefers Crystal, feels it's "tonier", but I am a little more casual than he is, and kind of like the more inclusiveness of RSSC. I don't think you can go wrong with either one. Awhile back, I was comparing prices for the same # of nights, and think Crystal came out to be a little more reasonable, even after figuring in tips, drinks, etc.
Love, Elena
