The 2012 cMBP's CPU performs better than the 2013's MBA's CPU. According to PassMark (CPUbenchmark.net), the cMBP's CPU scores at 3813/300 (score/rank) and the MBA's CPU scores at 3584/340.
Now, will you realistically notice the 6% difference? No, not in the slightest (especially in the context of your intended uses).
However! The MBA's GPU is much better than the cMBP's GPU (HD5000 vs HD4000).
Additionally, if you don't upgrade the cMBP to an SSD, it will suck compared to the MBA. But even if you do, a SATA III SSD will still get outperformed by the MBA's PCIe SSD (perhaps just slightly, but nevertheless).
Also, the resolution on the MBA is higher than the cMBP's. This is important for college because you'll be better off with having windows side-by-side (browser and Word whilst writing a paper, for example).
Lastly, the new MBA has twice the battery life as the cMBP!
So in conclusion, you'd be silly to go for a cMBP over an MBA.