It's tough. Overall, factoring in everything on balance, it's probably got to be Hogsmeade. Arguably the strongest attraction lineup in the park, coupled with detail-rich environments. Jurassic Park was once my favorite place to spend time, however (even after Hogsmeade opened), because of the strong atmosphere and ambiance in there. But who knows what it's going to look and feel like once the coaster eats up all the mood.
I really don't think there's a truly "weak" land in the park, at least from a design aesthetics standpoint.