I really like the DS Lite's D-Pad. I prefer the softer (but still responsive) feel of it compared to the Phat. The 3DS' D-Pad is very similar to it, but I think I like the DS Lite's a bit better.
TBH though the OpenPandora probably has just about the best D-Pad I've ever used, period. If it was on the list that would be an easy choice. The controls on that thing, minus the rather crappy little analog nubs, are overall some of the best I've used. Not counting the keyboard, just talking about the game controls.