light use of protools, web browsing
Since everyone is going into a Retina war - some apologists, some realists - I thought to just answer your question.
Your 2011 is fine. Put a Samsung 830 SSD in it, max out the ram to 16. It'll feel like a new machine at a fraction of the cost (Around $300)
All of the 2012 machines are having issues. I would keep what you have. There's honestly nothing wrong with it. If you're that committed to getting something new it really comes down to the weight: do those extra pounds matter? If yes, get an Air. If no, get a Pro.