I haven't measured, but I can't believe the 13" has a trackpad much larger than the 11". In fact, I'll bet they're the same size (or damn close).
Nope, sorry. They're the same width, but the trackpad on the 13" is 3" high, 9/16" taller than the one on the 11", which is 2 7/16". That's a lot.
BTW, I have the large, USB Trackpad to go with my extended keyboard with my 27" iMac. Makes the iMac feel like a huge notebook. Much better for my wrist than a mouse.
Tony