The only difference is the color and the graphics. The T-Mobile and Cingular/AT&T Pearls have always been different in this aspect. The coloring/graphics might make it appear different, but it's not if you check carefully. The keypads are exactly the same. If you want to know what a Pearl2 style keyboard looks like, check out the below picture:
http://www.phonescoop.com/phones/zoom.php?p=1368&g=1
Notice how the top 4 buttons are larger on the Pearl2 and there is no separator between them and the rest of the keys. Also notice how the top two middle buttons are attached on the bottom on the Pearl2.