Hi Bryan:
Looks like Arigram pretty much covered the bases in his reply. The one thing I would add, though, is that I still prefer the waist-level finder on my 500C/M because it folds down flat and makes the camera more "compact." That means I can go out with just the standard lens, 1 film back, the WL finder, and stash it all in a small bag cinched around my waist. The other finders would require a bigger bag and be less convenient when I'm just out for a stroll with my dog (and sometimes not even carrying a meter!). Perhaps you don't plan to tote it around with you like that, just it's a thought. Even if you buy another finder, you might want to keep the WL, too.
Enjoy your new camera!
Pat