Which macbook is right for me ?

Should I get

  • MBA 13''
  • 1.8GHz Intel Dual-Core Core i5, Turbo Boost up to 2.8GHz
  • 8GB 1600MHz DDR3L SDRAM
  • 128GB Flash Storage

or
  • MBPr 13''
  • 2.5GHz Dual-core Intel Core i5, Turbo Boost up to 3.1GHz
  • 8GB 1600MHz memory
  • 128GB Flash Storage

I am a student. I run Word, Excel, powerpoint. Occasionally I run photoshop, apature and iPhoto. I do alot of browsing and use iTunes to play music. I can't figure out if its worth the extra $400 to upgrade to the MBPr or can I get by just getting the air. Any insight would be appreciated. Thanks.