Get either the:
Vx, this is the cool, small palm. The screen size IS a hair smaller that the III series. The thickness is were this palm shines though.
IIIc, the readablity of the screen is incredible. In bright AND especially low light conditions the color palm is perfect to work with.
I used to have the IIIxe, it was nice... but I really didn't like it in the lower light enviroment, the Indeglo style backlighting still didn't cut it, so when the perfect deal came along on the IIIc I jumped and have been happy ever since.