I hear ya, CJ. That may be one of the most difficult decisions you'll ever have to make.
Personally, I am partial to the single row of one sheets, as double row is a little bit of "awesome overload", and because it's more like the way I've always seen them outside theaters, but then again when one has so much paper that is deserving of being displayed, double row is good in that sense. The space itself also dictates what goes where, of course, as I have a few walls where an insert frame is the only size that fits, or another where a 40x60 frame fits perfectly. For my one subway poster, I put it in an area that is in the farthest corner from viewing, as it's the largest in my humble collection displayed. Sometimes it's impossible to know how they'll look until they're displayed (at least in my case), and then they can be rearranged to perfection. Good luck.