I'm upgrading my old 2008* model and am going to buy used. It will, at the very least, be 8GB/256GB, but what are your thoughts on the versions and battery life on those. I think I'll stick with the i5, as the faster chip/gpu hits the battery. On an aside, is there an OSX equivalent of the iOS activation lock I need to be wary of? *I've had various work-issued computers so its not a big deal that my personal computer was slowish.