No wonder you're cramping, the xbox 360 controller is designed to be held by adult hands not child/dwarf/hobbit hands. 

Most xbox fanbois here love the joypad for the following reasons.  In most properly keymapped games, you never have to press both the lb/lt and rb/rt buttons at the same time.  You only have to designate the index finger for those buttons.  You can/should be using your remainding 3 fingers to grip the controller which fits snugly into your palm. Using the index fingers for the left/right triggers is supposed to emulate triggers for guns (which is more natural than using the middle finger) in shooters for example and providing better accelerator/brake control for driving games.  I'm sure other users can provide better examples.

the dpad being on top of the analog controller is a throwback to an era where you actually used dpad as the primary input device.  Users of the sega saturn(the first analog gamepad-which came with nights into dreams)/dreamcast/original xbox have always understood that the analog stick for movement makes the most sense as its the normal resting position for the left thumb.