Motorola Droid probably is the clear leader when you consider it's sales. The Nexus One is basically the current generation Android reference platform, just like Dream (G1) and Ion (MyTouch). Note that the Incredible and Desire are basically variants of the N1 and aren't really anything that different.

Basically your choice comes down to a hardware keyboard (Motorola Droid) or better specs (Nexus + variants).