Some of the 2013 ones only have 4GB of RAM which could be an issue. Other than that probably not worth the $200 for minor upgrades imo. Depends on which ones specifically you are looking at (endry level vs high end, screen size, etc).

Mainly looking at the difference between

http://www.bhphotovideo.com/c/product/1010898-REG/apple_me294ll_a_15_4_macbook_pro_notebook.html

and

http://www.bhphotovideo.com/c/product/1072689-REG/apple_mgxc2ll_a_15_4_macbook_pro_notebook.html

As far as I can tell they are the same aside from one having a slightly better CPU

Watch out with macbook pro

i have one and it heats a lot
its bad for gaming and extended video use.

however, it's a great computer for anything non-related to Gaming. (school is best for)

A good friend of mine own first one you listed above, and he's regreting buying it because of its overheating while playing any games. If i would be you, i'd better buy any other laptop for the same (lower) amount of money, or just build an awesome rig. It doesn't really worth spending 2k dollars on a laptop thats overheating while playing 7 years old game imo.
TLDR: What #5 said.

http://en.wikipedia.org/wiki/MacBook_Pro#Technical_specifications_3

My 2011 MBP sounds like a plane taking off when I watch twitch so I have to use livestreamer

Turn up the fan. I have a Early 2011, that I use for work and games, no issues.