From left to right: HP TC1100 (10.4” 4:3), Motion LE1600 (12” 4:3), HP 2730p (12.1” 16:9)
While it may not matter how big the screen is when reading reflowable, scrolling music (like with SmartMusic), it matters a lot when reading from scans. The biggest display for this kind of music is the 12” 4:3 screen of the Motion LE1600. While the HP 2730p is also 12”, you can see how much is lost by using a widescreen display with what used to be 8.5x11 paper.
None of these options is close to real paper though. I still think bigger would be better.