I did some real life tests today at the apple store comparing side by side the new entry level MBP 13" vs. a MBA 13". Here is what i found:
- opening certain apps is still faster on MBA 13" (itunes, iphoto..)
- safari opens possibly a split second faster on the MBP, its basically instant
now for a stress test, i opened itunes, played an mp3 with visualizer turned on, then open a vimeo video with HD on and full screen:
- MBA started dropping frames on the video, zero hiccups on the MBP
getting more hardcore, i open a new tab in safari and play another vimeo video at the same time, with HD on and full screen:
- MBA is dropping mad frames, still zero hiccups on the MBP
now super hardcore mode, i open a third tab in safari play yet another HD video at the same time, also open iphoto, imovie project & garageband, and play them all together ( sound was muted

):
- MBA vimeo video is basically unwatchable, MBP drops a few frames here and there but is still very watchable
Of course in real life use it's probably rare that one would stress his computer so much, but still this test concludes to me that the MBP 13" is way superior to the MPA 13" even with the so-called inferior graphics of the Intel HD 3000. The MBA is bottlenecked by its slow C2D cpu. The MBA was only superior in opening certain apps where indeed the MBP slow HD is the bottleneck..
(btw, I also performed the same test on a white macbook and it performed worse than even the MBA)
The real MBP downer imo is the screen, the higher res on the MBA gives it a significant better real estate, also the glare on the MBP is horrible due to the glass panel. At screen brightness 1-6 bars on the MBP, it was basically unusable in the store due to so much reflection, where as on the MBA, even at 1 bar i could read a web page fine.
For light use, i'd say the MBA is therefore a better option, but for power users that want a 13" there really isn't any alternative than the MBP atm ..