Very Nice photography! Interesting and insightful review too. FWIW, I've owned all reviewed here and a few more. My general thoughts after a 35 year active search for the perfect .22 revolver.
First, there is NO perfect .22 revolver. Only those perfect for a certain task for a certain shooter.
That said, I believe the K framed smiths have the best "shootability" of the dozen or so .22 revolvers I've owned. Better (and easier to tune )triggers than the Ruger's and J frames. Overall size and weight produce smoothest DA pull and follow up shots. ( J frames can be tougher to shoot accuratly.) Longer sight radius aids in accuracy.
Barrel length? I'd agree that the 4" 617's have better balance and comfort than it's 6" counterpart but not better than a 6" unlugged Mod 17. IMHO, the full lug is a disservice to these otherwise fine revolvers. Not sure I'm in love with the 8-10 shot options either. The shortened stroke definitely gives the DA function a "weird" feel for this old wheelgunner. My favorite 617 was a 4", no dash , 6 shot.
In conclusion, based on my experience, if I could have only one, my choice would be for an older mod 17 in 6" or (close second) 4" mod 17/18.