If the 13" rMBP had 1440x900 native resolution, I would consider it. I think the retina screen is nice to look at. But I'm not a fan of 1280x800. It would also be more appealing if it had a quad core cpu. I wish I liked the rMBP better, it is a nice machine, but currently the MBA is the best fit for me.
This is a stupid question, but what's the problem setting the resolution on the rMBP to 1440x900?
That's what I run mine at.