I recall one writer who's mounted over a dozen GPs in the Ransom Rest.....best group was .19" (no, that' ain't no typo), and found EVERY example would deliver at least one load under 1" at 25yds.
Go with the 4-inch barrel regardless which gun you choose.
I've had the GP100 3" and it don't stuff away in your britches any better than a 4" Blackhawk or GP... I respect the 4's.
Single actions naturally points high when I present them (aim) and I have to make a conscious effort to keep the nose down... It's the way the good Lord made me...I ain't very elastic in the elbows (1911's point best for me).
The only learning curve with the DA revolver is compensating for centrifugal-force of the whirling cylinder... which is why you see many folks reverting to cocking DA's.
If you get the Black hawk look into the "Gun Fighter" replacement grips.
I vote for the gp cause I like DA much better than SA. I sold my gp and have had sellers remorse ever since. That GP taught me to do a rapid double tap by usng the recoil. Make sure you practice in a safe place.
gramps