I haven't tried Sema, but of the other two I prefer the Pavillion because the food is generally better. The Thai Corner Cafe has a nice atmosphere, but the whole 7.30/9.30 thing I find really awkward. One's too early and the other's too late. Yes, Pavillion's a bit more expensive, but we don't have thai all that often and I think, given the quality of the food, that it's worth it. (I've never eaten in there, mind. Only ever had stuff delivered.)