: In terms of raw clarity at the output, the difference is going to drop off
: pretty quickly with viewing distance; if you're the sort of person who
: sits 10 feet from a 32" display, the difference in clarity will be
: rather subtle. Some people sitting closer might notice; if you're 5 feet
: from a 50" display, it's likely going to be visible.

The problem with all of these "it only matters if you sit so close" arguments is that the human visual system is significantly more complex than what is assumed. Our visual acuity can pick out much finer details in contrasty areas, as well as pick out fine details in motion. The idea that one you can't make out individual pixels means a resolution increase isn't necessary is simply not true.

: At the end of the day? Probably not a huge deal, but 1080p rendering tends to
: be a visible improvement over 900p.

I would say this is true all other things being equal, but if you are rendering at a lower resolution you can crank up the effects, which in terms of processing power are more bang for your buck than a resolution increase. Given the choice between a higher resolution, and better lighting effects / shaders etc, I'd pick the effects.