Macbook Pro Retina: 13 inch vs 15 inch

Hello all, I am thinking about replacing my old iMac with a new Macbook Pro. The only problem is that I am having trouble deciding on which one to get. I will be using the computer for normal every day use (internet, MS office, music, etc.) but also plan to run logic pro and various other games. I am alo looking at getting it with a 512 gb hard drive due to size of my music/movie collection. My question is whether not not the 13 inch will be able to run games like the new Sim City (launching this Spring), Civilization V, Bioshock, etc. Or should I simply go with the 15 inch model just to be safe. The other cool thing is that the local apple store in my city is currently offering a "last gen" macbook pro with a 2.6 ghz quad core i7, 8 gb ram, 512 gb hard drive for $2,299. However, I am not sure if the extra money is worth it in my case. I just wanted to see what the ole forum community suggested. Thanks so much