I've been considering the same question as the OP here and wonder if you care to elaborate on what the advantage is. Is it just that Wright's open end grips better, spreads less, or do you prefer how they feel in your hand better? They both seem to have a fairly thick beam and I know Williams Supercombos have quite the following here on the journal.
The best way I could explain it, is that you could take a wooden crate full of Wright combos, drop a nuke on it, and return to find a bunch of unharmed, dirty looking wrenches scattered all over the place.
I had a few sets of full polish Wright combos, and they had some of the nicest overall chrome and finishing I've seen on any wrench, including Snap-on. I've seen the standard satin Wrightgrip combos recieve SEVERE abuse at work, and I've yet to see one fail.
The fitment was spot on, and the average Wrightgrip wrench that I've seen has better formed gripping ridges than the average FD+ wrench that I've seen. OTOH, SO's sockets beat Wright's in overall fitment, so it's kind of a wash.
The ONLY reason I own SO FD+ now instead of Wright, is because Wright has a few holes in its size lineup that really bother me (11/32 in particular). Yes, I'm OCD like that. I wish I could help it, but it's an uncurable disease.