I mentioned this a little in the Pete Dye thread, but I do think the architecture has a lot to do with it. The PGA schedule is rife with courses that certain players clearly seem to favor, look how many wins Tiger has wracked up at Bay Hill, Torrey, Firestone, etc. Look how Phil plays Pebble, Torrey, Phoenix.
This is not true of the TPC at all. The best players win there, but not all the time. Unknowns or little-knows can win. The past winners include bombers and short knockers alike.
The course tests the whole game. Length is sometimes rewarded but not to the exclusion of accuracy. The penal hazards and, perhaps moreso, the small greens make bomb and gouge a poor strategy. So you have to hit it in the fairway. Then you have to get it onto those small greens. Even then you have to putt well on greens that are not as dramatic as they once were but still have plenty of interest.