The 686 Pro is my wifes. We shoot steel matches and ICORE with the 7 shot guns. I lucked into the PC gun sitting in a shop last year NIB.
Other than one gun has an 1" longer barrel, they shoot the same.
I've used her Pro last year in a match, and really liked it.
They both come ready to accept moonclips, so thats a big help for match shooting. The Pro is going to be a lot easier to find, than the PC gun.