MacBook Air vs MacBook Pro retina

I need a new laptop. I have been using my ipad as my main computer but it doesn't always work well as my main computing device. There are things that I still need a computer to do. Not everyday but here and there. I am a college student and have been typing my papers on this ipad. I have decided I wanted a Mac an 11inch. The thing is choosing between the retina display or battery.