Which should I buy: Air or rMBP?

I think I'm going to purchase my first Mac soon, and I've narrowed my choices down to two refurb models: a 13-inch 2013 Air and a 13-inch 2013 rMBP.

I use my computer for school, web browsing, as my main mode of watching TV shows, and maybe 10 minutes of Portal once a year.

I guess the main questions I have are as follows: Has the processor and graphics upgrade from the 2012 13-inch rMBP to the current model alleviated the stuttering issues? Is a retina display even a big deal in the first place seeing as I do no editing and I'm not sure most web content has been optimized for it yet? Should I be worried about the new low-end rMBP only having 4 gigs of RAM?

They're both the same price so I really don't know which one I should buy and any help making this decision would be appreciated!

Feel free to chime in with any points I haven't brought up that you think would affect my purchasing decision.