You mean your store doesn't have a 1080 display to show off NBA 07 in all it's glory???
The progressive means it has twice as many scan lines as interlaced, thus looking better. Interlaced renders every other line:
An LCD won't show this accurately, just stand across the room and look at the monitor to get the idea of how it'd look on a TV.
IMHO, NBA 07 looks like a higher polygon and more lighting (not necessarily better) version of NBA Live 2005 with Live 2002 animations. And the gameplay is pretty trashy.
How significant is the difference betweeb 720 and 1080? Resolution-wise?
Just do it like you would on a computer...
1920x1080 vs. 1280x720 (regular TV is 720x480 for NTSC or 720x576 for PAL)
The closest standard resolution comparison, (in terms of increase from one to the next) would be to boot up a game, run it at 640x480, then at 1024x768. That'd be close to the 720 to 1080 jump. (800x600 to 1280x800 would be the actual closest I can do with my monitor, but that second one isn't a standard resolution)