[MacBook] Air Core i7 vs Pro Core i5

  I've got a 6 mo old 13" Macbook Pro with the 2.5ghz Core i5 processor. I'm thinking about getting an Air. I'm looking at both the 11" Core i7 and the 13" Core i5. I know the 13" 1.8ghz Core i5 isn't going to compare with the 2.5ghz...