Hi guys, I'm looking to buy a MacBook Pro. I'll mainly be using it for web design/development and mobile app development. It'll be hooked up to an external monitor in my office (1080p) most of the time. I'm not sure whether to buy a 13" or 15" MacBook Pro - older model or even newer Retina model. Any advice would be welcome. Would I need a higher resolution than 1366x768 for web design?