Need some help. If you had the choice would you buy a second hand late 2013 15" rmbp with 512Gb and 16G Ram for £1100 or pay £1079 for a brand new late 2015 13'rmbp. It is mostly for photography processing in Lightroom and Photoshop although I also own a GoPro and will use this a lot more this Summer. The only thought I have against the 15" is that it is second hand with no warranty and the 13" would be brand new. I don't want to let up the opportunity to get the second hand 15" if folks think it would be far better. My main machine is a Mac Mini 2.3 i7 with a 512 SSD and 16Gb RAM The screen size is not a deal buster..... Your thoughts as I don't know which way to go ???