Since most sit and goes pay the top 3 places on a 10 person table I'd say they have the best overall payout possibilities. If you're on a site like PokerStars, remember that a high payout field event will pay far less than the buy-in until you're about 1/3rd of the way into the payout field. Low payout fields mean more $$ for each place paid, even the early ones, so I'd say they are probably the better deal. Percentage-wise though, S&Gs offer the best chance at a payout.