This is Coke or Pepsi. Do this... call up your music supplier, have him send you both mics. Return the one you don't like. Just tell the dude up front what you are doing and they are usually cool with getting one returned. I am an SM7 fan myself... but I have heard plenty of great tracks on an RE20 too. (I should probably get an RE20 someday just to have around in case.)
Also, for Foley... well, you might want to look at some lower cost SDCs. Heck, for Foley work, you can really do a heck of a lot with a pair on cheapish SDCs. Check out the Naiant omnis, especially the X-Q.
http://www.naiant.com/studiostore/microphones.html