BlackBerry Pearl 8100

Hi, I have T Mobile but I really like the red pearl offered by AT&T. It seems the features are different like the set up of the screen. When you cordinate it with T Mobile will this change to the T Mo version or is this just built into the phone itself? EX: Like on T Mo the icons are at the bottom if you like but with AT&T they are all over the screen. Also, does anyone know if I do purchase the red BB can it really configure with the T Mo version? Will I be able to have the browser, email, and MMS?? Any advise would be greatly appreciated! Thanks