Hi xShane,
Let me apologize first of all: I did not read through all of the posts in this thread, only your original posting, so if someone else has already suggested this, I apologize for repeating it.
Your eyes are too good (or you are too young - probably both)! Meaning that you can sit farther from the display and still see it fine, unlike us old farts. When you are farther from a display screen, then the individual pixels are smaller, in terms of their subtended angles, than the human eye can distinguish. If you can't distinguish the individual pixels visually, then you won't notice much difference between the displays. That is to say, you won't notice the resolution differences since your eyes can't resolve the actual pixels, but you still might notice a difference in colors, blacks, and contrast.
I believe this is what often happens when someone visits a Best Buy and views a rMBP sitting next to a uMBP or even a cMBP. You just naturally are farther away from the screens when viewing the Best Buy display (at least this is true for me, because I'm too much of an antediluvian troglodyte to stoop down as far as I would need to in order to be at a natural viewing distance to the laptops) than you are when sitting at your desk actually using the laptop. And since you are farther away when comparing the Best Buy display models, both the 110 PPI and the 220 PPI screens have pixels subtending angles too small for you to distinguish from the greater distance -- i.e., both displays look more-or-less the same.
...just another thought...
Regards,
Switon
P.S. (By the way, the subtended angle distinguishable by the human eye is dependent upon the physics (optics) of the human eye, especially the size of the pupil (aperture) which depends upon the intensity of the illumination light as well as the age of the person -- the older you get the smaller your maximum pupil size. Believe it or not, but a smaller pupil allows for a smaller subtended angle to be distinguished since there is less "confusion, blurring" in the focal plane with a smaller aperture. Rather, a young person is favored because the young person's eye can focus (more flexible lens) over a greater range than an older person, thus allowing a young person's eyes to be more accommodating to visual distances, excepting in the case of a hyperopic oldster.)