A classic 2012 MBP provides noticeable better viewing angles and colors than the 2014/2015 (maybe 2013 too) Air.
Interestingly, I have both. I'm not sure I'd characterize the 2012 MBP display as "noticeably better." As I've noted, I find the display roughly equal to that on a 13" MBA.
You folks cavalierly ignore the UI lag and decreased battery life that will inevitably result from trying to add a retina display to the MBA. Are you really more concerned with the display than with overall performance?