So I guess it comes down to blued w/ 6 rounds or stainless w/ 10 rounds. Decisions!
There's also the question of barrel length. I could go with the 17 with its 6" barrel, the 18 with 4" barrel, or the 617 with either a 4" or 6" barrel. For the purpose of improving my marksmanship skills, would I be better off with a 4" or a 6".
I have both - a 1951 6" K-22 and a new-ish 4" 10-shot 617. Between them, the 617 has the better balance of versatility, accuracy, capacity and ease of maintenance, so if I had to choose one, I'd choose the 617.
The 4" barrel is more versatile - it's not only a great plinker/range/teaching gun, it serves as my understudy to my IDPA 4" 686, too. I've also used in rimfire steel matches, and gives up little in
practical accuracy, so I wouldn't hesitate to use it in bullseye. If the local laws allow it, it'd make a fine small game gun, too.
My 6" K-22 and 4" 617 balance well, but a 6" 617 is too muzzle heavy for my taste. If you're as accurate with a 4" as a most are with their 6", by definition, you've learned to do a better job establishing and executing a proper sight picture.
I like the classic look of a blued gun, but I shoot my 617 so much, it has to get cleaned often, and stainless is easier to clean & maintain.
I also prefer the 10-shot capacity over the 6-shot. It also makes it easier (or even possible) to shoot in rimfire steel matches with it (there's that versatility thing again). And cleaning 10 chambers doesn't take much more time than cleaning 6.