I need something to last me through college classes on battery so I'm planning on purchasing either a MBP 13 or 15. Probably refurbished. So whatever size I choose I have the option of a 2010 model and a 2011 model. I'm assuming 2010 and 2011 will have different software, I've been hearing bad battery life with Lion and it sorta worries me. So: What has better battery life - 13inch or 15 inch? What has better battery life - Old software vs new? Also, if I go for the 15 inch: April 2010 has 2.53GHz i5 & graphics of NVIDIA GeForce GT 330M graphics with 256MB of GDDR3 memory while the Feb 2011 has 2.0GHz i7 & Intel HD Graphics 3000 & AMD Radeon HD 6490M, for $100 more. - Huge difference between the two? Thanks!