I bought a refurbished 15" MBP released April 2010. It's spec is 2.4gh(i5)/4GB RAM/320 GB hard disk. Which is very similar to the new low end 2011 MBP 13". I'm mainly going to use this MBP for software development but I was wondering if the new SandyBridge based i5 cpu is a better for programming than the last year model. Should I return the refurb and get the 2011 13" MBP? How many of you use your MBP for software development and what do you think?