mainly the pro has a faster cpu and more memory both hard-drive and ram, but the air will have faster hard-drive thanks to its ssd instead of hdd, means virtual memory like a flash drive instead of a disk spinning fastly watched by a laser, ssd's are close to if not over twice as fast on loading into windows alone, thanks to the ssd, i'd take the air cause it's ssd will make everything faster, and the pro has a slow hdd too but almost all lappys do, but at the same time i like things with some wait to them and i like faster cpu's so i might take the pro
you can compare them here and see all the prices cuz they have cheaper ones, but also i'd tak a pc first, better for gaming and cheaper for same exact computer without the aluminim case which is nice.