Which is better? Mario and Luigi Superstar Saga or Partners in Time?

IMO Superstar Saga was a lot better. It really took the Mario series in a new direction, rather than Partners in Time, which was really just more of the same. In terms of gameplay, they are both pretty similar, but the addition of Baby Mario and Luigi in Partners in Time was a welcome change. However, I think the decision to keep Fawful from center stage was not a good idea, but then he did get a major role in the third game, so that's good.