I have never agreed with the "Waters era" vs "Gilmour era" thing, since Gilmour was also in the band the entire time Waters was (except for the very, very beginning) and had a big part in their sound and songwriting. Yeah, Waters had the grand concepts and wrote the lyrics, but it wasn't the "Waters era". If anything, it was the classic line-up versus the various fragments that were left when there wasn't enough room for Waters' ego and the other four.
Once Waters left, the magic was gone IMO, so I'd say that that's a strong argument that it took both of them together to make the magic. Therefore the answer is Mike Portnoy.
Nah, just kidding. Gilmour.