I've had both and compared rather extensively because I'm a screen nut. I've seen and compared the MBP LG 9c81 and 9c82 (or whatever it was that came before it from Chimei) and the MBA XX73 (AUO) and 9c6F (Chimei).
Contrary to what many people are saying about the AUO MBA screen, I actually don't think it's very good except for being very bright. Given how small the display is, the backlight is not very even (In addition to my own I checked many units at the Apple Store and they were more or less similar and notebookcheck.net measurements confirmed) and are darker in the lower right corner and sides compared to the middle. They also have noticeable surface coating 'graininess' that can easily be seen if you drag a white or light window across the screen. By comparison, the macbooks have no grain and the MBP LEDs have close to none. In terms of uneven backlighting, I think the AUO and LED MBP displays I've seen are comparable, but the LED MBPs may be a little better. Because it's smaller, unevenness seems less visible. On the other hand, the MBP has the lower 1/3 yellowing problem that seems to be a hit or miss thing.
Viewing angles are about the same on both. The best MBA screen I've seen is the one manufactured by Chimei (strangely, given how bad the 15" Chimei displays are) - it is more evenly illuminated than the AUO one and seems to be close to the macbook in terms of graininess - very smooth, bright and consistent. I loved it and thought it was much better than the AUO.
So, on balance, I think they're both good but each has its own issues. Of course, this is my opinion based on seeing/owning a limited number of MBPs and MBAs.