I went shopping today, looked at a 617, a 63, and the all aluminum 317, and a GP100 .22LR. Here are my impressions:

Model 63: Very nice for a kit gun or practice for shooting your J-frame. Solid, well balanced, and feels great in my hand.

Model 317: It weighs nothing! As some have said, it may be pretty tricky to hold your aim with it so light. I'm sure it has a purpose in life, not quite sure what it is.

Model 617 - the Beast: Clearly of impeccable quality, this was the 6" and that massive fully shrouded barrel certainly makes it muzzle-heavy.

GP100, .22LR: Excellent quality, much better balance than the 617. I like being able to stage the trigger in double action, so this is probably the one I'm going to end up with.

They didn't have an SP101 in .22, but I've handled that one before. It's not bad, but not fabulous either. They did have a 4.2" in .357 that felt kind of loose, not as well put together as my 2 1/4" SP101.

Originally I was looking for a .22 to practice with, to save money on ammo. But that's evolved into wanting a nice .22 for precision shooting. I know you can't beat a 617, but the GP100 isn't far behind.