Both good objective opinions. While the GPU and CPU are much slower in the 13", I think many would be surprised how well it handles stuff. I kind of hate the idea of tinkering with an aftermarket SSD to be honest, although RAM isn't a big deal.
I do very very occasional FCPX, Motion, Compressor, and Photoshop. I do not game one bit, so that doesn't bug me. I've ran those programs on much older and slower machines before to a somewhat decent level.
I have the 13" as I'm typing and I love it. But I wouldn't mind a bigger screen as my only computer. Just wondering if I'm going to be kicking myself for not getting the quad-core.
I upgrade every couple years.
EDIT: I should just find the extra money and get the refurbished 15" rMBP. (I got this one with an employee discount, but I'm at my return date with it, and the extra $150 or so for the 15" retina would put me tight financially right now. No money lectures please

)