Retina stole the show, so the 13's just arent the "fashion" at the mo in the media.
I had a 13" for 2 days from John Lewis after babysitting a 15" 2012 MBP and I almost kept it but it was just too small for what I wanted it to do. I'm now looking after a RMBP and to be honest I prefer the "meaty" URMP's with their proper on power button and the battery green diode display. Plus you know youre holding it either in 13" or 15" guise as the shape and feel is like a chunky chocolate bar compared to a wafer thin mint.
The RMBP base model is good in some ways but just rubbish in others...what can you do with 256gb of hard drive now days? The screen is really nice in OSX but scrolling is still not that smooth (even with updates) and certain websites look a little off. Try Win 7 in bootcamp and its either to small (for me) or not quite right at 1920x1200. The glass screen isnt as reflective as the non-retina mbp, in fact I dont get a reflection at all so thats a bonus. Its fast, but how much faster than an mbp with an ssd of equivalent spec I dont know and I doubt fast enough to notice. Im also curious to know what graphic designer/professional photographer would really want to be working on such a small screen in the first place to take advantage of the screen, most of the professionals in this field I know of want large screens to work with. I guess in the field its useful but to the average Joe its just a Nice/expensive feature to have. Its absolutely a great piece of engineering the rmbp and one that Apple need a big nod from the rest of the PC world and Im sure there will be more to follow.