Parallels or Bootcamp?

I am considering purchasing Parallels Desktop 8 for Mac and install it on my 2011 MBA i5 256GB w/ 4GB ram. I don't know very much about the pros and cons of using Parallels vs Bootcamp... My purpose for downloading windows is to:

- use MS Office

- Mathmatica

- install a game (maybe)

Also are there any issues with drivers? (is Windows 7 more stable?)