This is greatly generalized...
If you want portability and can rely on wifi only, no optical media and basic tasks (mail, music, surfing, productivity), go Air.
If you want performance and portability go MBP 13" (with an SSD, mine weighs in around 4.1lbs, 1.2lbs heavier than the Air).
If you want real performance, go MBP 15".
----------
If they refresh the Pros as above, I'll sell my current MBP and upgrade first week.
MBP 15" is way too big for me lol. When do you guys think there will be a refresh of the MPB or AIR?