I'm with Cnad here. Bigger is better.
The caveat I was told about large displays/screens is to prevent 'having to scan with your eyes' from side to side the images on the screen. Although this is unavoidable in theaters at times, but a consideration for one's home setting.
I sit about 8-10 ft from a 59 x 99 or so inch, screen so i CAN SEE IT AS WELL AS POSSIBLE. I got roughly $900 or so in the DLP PJ and DIY screen and I'm pretty happy with it as it suits my own more 'special' needs best. I think that's the ticket always too. Suiting your own prefs and needsn in the areas of video and audio rather than the projected or presumed needs of others by compromising those of your own.
Eye strain, and eye fatigue are worthwhile considerations. So the bit about not having to scan repeatedly, the screens images to gather it in fully however does seem a noteworthy item, given you have good enough vision to begin with I'd keep that in mind.... yet still, big and bigger to a point is sure better. I get a bunch of Wows! from others when they view mine, including my own "yep, that'll work!".
...and yes I can control the lighting entirely, though my own situation allows for some light without degrading the color or image significantly by all accounts.
Good luck.
