You lose out on the retina display, thats your issue. They have also updated the 13 inch rMBP to broadwell, with force touchpads. If you are thinking a dual core computer the rMBP is still the best all round package.
Ok, having just looked at the price difference with my student discount i think the Macbook Pro 13" would probably be the better option.
Macbook Air "13 maxed out £1245.60 (2.2Ghz, 8GB Ram and 512GB SSD)
OR
Macbook Pro 13" £1,203.60 (2.9Ghz, 8GB Ram and 512GB SSD)