Almost certainly going to be the base 15 retina model except upgraded to 16GB for me.
For 256GB SSD storage and 8GB RAM, there's only a $100 difference between the 13 and 15 inch models in the educational channel. And that gets you quad core, the bigger display, the better speakers and discrete graphics. Dropping in the extra RAM to 16GB (the $180 cost is ridiculous, but as it's not upgradable you're kind of stuck with it) isn't even an option on the 13-inch, which arguably could use it even more given the lack of discrete graphics.
The 15-inch Retina has the best external display support this side of a Mac Pro. And the built-in display is good enough it enables me to get by without adding another color-critical monitor. The $500 upgrade to 512GB SSD is ridiculous, as much as the cost of buying a top-end Samsung or Plextor 512GB SSD on its own, so I'll just deal with extra storage by using external.
I'm not real happy about having another 15-inch computer, but the 13 rMBP is overpriced and underspecced while the 13-inch Air has an inadequate display and both 13-inch models would leave me needing an additional external display, a color-critical one in the case of the Air. And I will now have two very fine 15-inch machines for the next few years, my Sandy Bridge hi-res matte replacing my old Penryn model for backup and the Retina as my new primary. One for home and the other for work.