I agree; the Grand is the only one that is really worth a special trip to see. The Gingerbread Showpiece is quite impressive and finding the Hidden Mickeys is something fun to do.
The DLH has a few trees (there are themed trees in each of the towers), but it doesn't seem to have a showpiece. The trees and decoration in the main building are pretty standard Holiday-decor; nothing about them really said "Disney" to me. The Santa M&G is supposed to be modern/contemporary, so it looks more sleek than holiday-ish. The PPH has a big sea-themed tree in the lobby (which is also the back drop for the Santa M&G) and some wreathes. Overall, I'd look at the DLH and PPH if you're already there, but I wouldn't make a special trip to check them out (or if you do, it doesn't take very long to see the holiday decor because there isn't very much). There are also some trees/decoration scattered throughout DTD. Nothing really major, but easy enough to see as guests walk through DTD.