I would say the S/V kiss hands down...now, if it had been Jack and Irina, S/V would have had some competition for the best kiss of the show! I enjoyed Jack and Katya's kiss, and Jack's reaction to it, but the two of them don't share the same kind of history as Syd and Vaughn and Jack and Irina, therefore, there wasn't as much emotion behind it. Unless, of course, we find out later that Katya is just Irina with plastic surgery or something...that would explain the more passionate kiss. But yeah, I'm going to go with the S/V kiss as the better kiss.