I had one some years ago. Nothing at all wrong with the gun, I just traded/sold it off later for something else. Mine was a 44 Special. It came in a wood display case with a glass front, with the S&W logo etched on the glass. Really nice looking.
Couple things "wrong" with it. The stock grips were round butt, smooth, THIN, "combat grips." I hated them, and replaced them with a Hogue grip, which played into the second thing "wrong" with it. That screming yellow chicken on the sideplate. I thought that looked tackey. Everyone else might love it, but I didn't care for it. Luckly the Hogue grip covered over most of it. And those Hogues gave the gun a "serious business" look and were much better with the recoil. Picture a Model 10 on Steriods.
The last thing is something I never thought about, have heard others complain about. The cylinder was the same size as the cylinder for the 44 Magnum, but was only chambered for the 44 Special. Why not chamber it for the 44 Magnum if it was the same size gun? Well, like I said, I never really thought much about that, since I shoot 44 specials in my 44 magnums most of the time anyway.
I consider those to all be minor grips, one, the logo being downright pickey. I wouldn't mind having one today.
Oh by the way. If my memory serves me, the Model 21 was in 44 Special, the Model 22 was in 45 ACP. Same gun otherwise.
Edited to add: How does it compare to a model 24? Well, the obvious thing is the sights. Model 24 has adjustable, Model 21 has fixed. The Model 21 also has a (IIRC) an old fashioned "half dime" type front sight. It was OK for me, but then I never try any long distant precision shooting. Other than that I never noticed anything really different. The Model 24 has a smaller cylinder for the 44 Special cartridge, whereas, according to at least one reviewer the Model 21 has the full length 44 Magnum cylinder. As I said, if that's true, I never noticed it. Model 24's came with better grips. But as far as a "gun" one is just as good as the other.
