I've hunted with both, and with a .460 S&W Magnum.
The .44 (6" barrel) is pretty much only a wild boar gun for me. I've used it a lot. I put a red dot on it, but I find that I can find and aim with a fiber optic front sight a little faster, particularly in the bright sunlight aiming into shade. I wouldn't mind hunting whitetail with it, but never have. Red dot or scope, probably no difference, though I prefer the precision of a reticle. I try to limit any shots to 75 yards or closer, but it will do 100 yards. No more.
The .500 (8" barrel) works very well for 100 yards or more. It was scoped with a Burris variable (1-4x, IIRC), but I've since moved the scope off. I tried a red dot on it once at the range, but the red dot did not survive the first cylinder. It is, I think, overloaded for whitetail, or even big boar. The really hot loads are overloaded for everything. I think that's deliberate on S&W's part. Recoil is, well, "stout".
The .460 seems perfect for handgun hunting, to me. I can download for small stuff, upload for elk, and scoped it is good from contact distance to 150-200 yards, theoretically. I've got it set and ready to go this Fall, scoped with the Burris, sighted in at 100 yards, with the 150 and 200 drop identified on the reticle. How soon to October?
As to your question on barrel length, I've always gone with 6-8", believing that the loads required that much length to get velocity up. I also like the increased sighting plane. And a red dot or scope would look weird on a short barrel, IMO.
I've never shot a Ruger; can't help you there.