My first SA was a .45 convertible Blackhawk... it was fine, until I found one of the new 5.5" SS .45 Bisley Blackhawks. I never considered the BHG until three years ago, when I shot a 3.75" .45 BHG Vaquero. I really liked it! I have medium-large hands... and the ball-like BHG just fit me quite well, as did that Bisley.
I soon bought a 4.6" SS .45 BHG Vaquero, a closeout goodie. It started a trend... next came a .357M sibling... then a .44 Magnum. The latter wasn't a 'stock' item... I ordered a QPR BHG via Brownell's, and fitted it to a new 4.6" SS .44M Super Blackhawk. I did sell the .357M BHG Vaquero - it just wasn't 'fun' to me. Finally, earlier this year found me getting a similar 4.6" SS BHG SSM in .32M. My Bisley and regular Blackhawks are long gone - my only SA's are the .45, .44, and .32 - all SS 4.6" with black Micarta BHG's. I like the BHG...
As to function: The BHG pushes it's ball-like shape into your palm - and along your arm as it's line of action - under recoil. There will be some muzzle rise, of course, and it is not restrained by your fingers, as in a plow handle shape. It causes a 'roll' in the round handle in your grip, not bad in the .32 or .357, a bit more noticeable in the .45 with 'cowboy' loads, and downright 'interesting' with .44 Magnums. The hot UMC 180gr JHP's in .44 Magnum give your palm a decent thwack and will 'roll' the muzzle skyward, presenting the hammer's spur to your hand's backside. Admittedly, I converted the SBH mainly for .44 Specials and Russians.
A great first thing to change on a BHG Vaquero is the hammer. I put Bisley hammers in mine, but they require some grinding and polishing in non-functional area's to fit - the SBH hammer is generally a drop-in. With the lowered hammer spur, you can easily cock the hammer with your shooting hand's thumb. The .32M still has it's original hammer... for now.
I would compare the Ruger interpretation of a BHG carefully to the Colt clones' 'original' BHG's. Like the original Bisley grip, the Ruger 'interpretation' is quite different. I like both of them better than the originals. You really have to 'try' them first... they really are quite 'subjective'. As to caliber and barrel length... I have let numerous folks, male and female, young and old, shoot my .45 BHG Vaquero at the range with 'cowboy' loads... they have all enjoyed the experience... except for my 5'10" wife - she said the grip was too small - prefers shooting my 5.5" .45 Colt Redhawk. As to length, the 3.75" is cute... but has a shortened ejector that won't always get the cases out with you pulling them out by hand. It also has a flush-headed cylinder base pin, which, in my experience, only comes out when easily when you don't want it to - under recoil! I like the less than an inch longer 4.6" barrel - with it's standard ejector and base pin.
Whatever you do, try one in your hand before buying it... and remember, they aren't copies of the 'original' Colt design.
Stainz
PS The hammer change was 'illegal' in SASS events.