MC, being able to shoot both guns and compare would be ideal, as I said. Failing that, holding both guns in the shop is next best. It can give you at least some idea of how well the grip(s) fit your hand, balance, where it "points" etc. It's better than buying blind.
My point is, that unless point shooting is your prime concern, how the gun "fits" your hand is superfluous to how it's going to shoot. It ain't like it's going to fall out of my hands, that I cannot grip the thing well enough to aim and fire it. What's important is that it's accurate.
Now, if we were talking defensive firearms, you MIGHT have a point, but I can get used to anything, frankly. I don't particularly like Tokarev grip angles for point shooting, but I can hold it without it falling out of my hands. I can even fire one and hit what I aim at. I shoot all manor of autoloaders and DA wheel guns, worlds apart in grip and grip angle, not a problem, I adapt, don't need to adapt the gun. Practice makes perfect even point shooting.
But, BP guns don't need to point fast and well, they're not about self defense. They should, however, be accurate. I have been shooting handguns for over 40 years and BP for over 35 and I haven't really found the handgun I cannot grip well enough to aim and shoot well with it. There is no instance that a gun was not useable for me simply because of the grip or "feel". Edit this, the NAA mini revolvers need a larger grip. I can't even get a finger around one to hold it steady, but I have folding holster/grips on my 3.
People have this same complaint about Glocks. Well, ya know what, I can shoot a Glock. Don't really like 'em for other reasons, but I never had one slip out of my hand due to the feel of it.
And, one of the absolute worst FEELING guns to grip for me is a 1911. Yet, I've won shoots with 'em. I can improve 'em with fatter grip panels, too.
If "feel" is important to you, all I can tell ya is you'd better pick some gun models up to compare, because everyone's hands are different and what one shooter prefers another scorns.