How is the processor on the 2010+ 13inch Macbook Pros compared with the 08 2.53ghz? I was hoping to spend in the $600 range and this one stuck out to me because it had the 9600m which is better than the 320m, but not as good as the 330m (though that one is a little out of my price range). I read that the 08 unibody model was pretty much the same with the early 09 model, but not the mid 09 which has the 2.66ghz. Would it really show that big of an improvement? I also read that the resolution is better on the 15 inch compared to the 13 inch and that if I was to game, then the 9600m with dedicated GPU would be better.
The cMBP-15s will definitely be better gaming platforms because they all have dedicated GPUs. I think there may have been issues with the 9600m though so do your research.
As for resolution, the 13" is 1280x800 and the 15" is 1440x900 in standard spec and 1680x1050 in hi-res spec. They all look very good and its really just a matter of screen real-estate. For my 40+ year old eyes, the higher res screens get hard to read so 1280x800 is best for 13" and 1440x900 for 15" screens.
The 2010 is a little bit of a tweener because the cMBP-13 still used Core 2 Duo processors, but the cMBP-15 moved to i5 and i7 processors (but all dual core). The real performance jump happens in 2011 where the whole cMPB line goes Sandy Bridge for a significant performance jump, the cMBP-15s get a quad core i7 processor, and all three sizes get Thunderbolt.
The moral of the story is: save a little more if you have to and get a 2011. It'll be worth it in the short and long run.