Video encoding is in fact dramatically faster than on a dual core.
You are explaining your rationalization for what you bought and not answering his concerns. All too typical of forum posts.
I do realise that video encoding is dramatically faster. But from what I understood OP won't be doing it very often. Really, the few minutes every couple of weeks don't quite cut it in my opinion. If we were talking about regular video editing and encoding then I'd definitely have said go with the quad-core 15" rMBP.
Also, when I was writing that post, I still had the feeling that OP really needs the mobility and given the non-intense workloads I figured the MBA/13" rMBP would be a much better option. Things have apparently changed since then, so don't accuse me of throwing around useless posts, as I tried addressing OP's concerns rather than trying to justify my purchase (that I really feel no need to anyway, because it was thoroughly thought out).
SarcasticJoe said:Sure, some (lazy) people think it plus the note materials and occasional (hardcover) textbook are too much, but if you have a good backpack I don't think it's that bad once you've gotten used to it. The days I don't have the Macbook with me don't feel that much tougher than the ones that I do have it with me. However I can understand the appeal of the now much cheaper 13" rMBP for people who don't need the graphics boost and wouldn't fault anyone for buying one because of the price.
I use a bag rather than a backpack and trust me, it makes a massive difference. Not to mention how nice it is to be able to just pick it up with one hand. But I absolutely see your point, get whatever suits your needs best... The OP seems to have made an informed decision and I'm sure he'll be happy with the machine. I personally wouldn't, but who cares if it's not me using it