My old Security Six was a strong, accurate revolver. It was a little less than accurate with .38 special, but was a tack driver with .357 loads. It kicked like HELL, though. Lots of muzzle flip. I really don't miss that part of it.
My SP101 is SWEET! It's very accurate and, weirdly, a lot easier to shoot with hot loads than the Security Six was! Not near as hard on the hand and no more muzzle flip. The SP101 is a gem. I would highly recommend it to someone wanting a powerful, easy to belt carry, accurate .357 magnum personal defense weapon. It is among the best choices out there for such a weapon IMHO and is the lightest .357 I can shoot well with full power ammunition. If you're going to carry a .357 revolver, there's no sense in shooting "light magnum" loads or .38 +P in it. Get a .38, cheaper. If I'm going to carry a .357, it's going to be with eyebrow burning, hog stomping, full power blow 'em in half 600 ft lb or better ammunition. I ain't messin' with those wussie loads for girls.
The SP101 fires my 180 grain handload to 1306 fps. That's 662 ft lbs!
That's enough for outdoor carry in bear country and it's quite accurate with that load, too. My defense load involves a little tamer 140 grain Speer at 1335 or so fps. It makes about 550 ft lbs from the gun's 2.25" barrel. I don't think you'd wanna fire this stuff in a Scandium revolver. I know I wouldn't.
Never owned a GP100 or Redhawk, but if I wanted such a handgun, I wouldn't hesitate to get one from Ruger. Strength and reliability and accuracy are the trademarks.