I'll be getting my first Mac ever later this month and I've been pondering the same questions myself.
At first I was thinking about the 11" Macbook Air but the 128GB model wasn't that much cheaper than the 13" and then I figured that getting the extra battery life and built-in card reader (I use SD cards a lot) would be worth the added "bulk" - if there's even such a thing on an Air. I've been comparing the two in an Mac store nearby and the 13" Air is still pretty tiny.
Then I thought to myself, if I'm getting a 13" maybe it'll be worth it getting a 13" Macbook Pro instead? It'll be a bit thicker but I'll get the extra performance to boost, right? As it turns out that doesn't really appear to be the case. Sure you get a faster CPU with the Pro but that's not as important for me personally, what I did find interesting here is that you're getting the same Intel HD Graphics 3000 with the Pro model, but you're actually getting a lower resolution screen and with the SSD the Air might actually feel faster in a lot of cases despite the slower CPU.
My question is, what's "Pro" about the 13" Macbook Pro? For me it's a lot less appealing than the new 13" Macbook Air. Obviously you might feel differently but this was my line of reasoning at least.
Right now I'm trying to decide if the 256 GB model is worth the extra money, should I go all out and get the i7 model or is the i5 good enough for me? Decisions! D: