I've been a huge fan of Rugers for the past 25 or so years. I've loved all that I've had - and I'd bet that's probably been a couple dozen of them.
Prior to this 617, I've only had two S&W's - both the Model 63 kit guns. Those were smallish and I had them more as "carry in the tackle box" or "fishing vest pocket" guns. I never took the time to tinker with them.
Now that I've had a chance to take a S&W apart and tinker with the insides..... I'd never buy another double-action by any other manufacturer! Like I've said, it just begs to be polished! And you're rewarded with silky smoothness!
The single-action trigger is lawyer-heavy from the factory. But with a bit of care.......
On the subject of barrel length..... Yes, The 4" does give a better balance than the 6". But if you're like me and enjoy plinking and hunting with open sights, the sight radius on the 6" is about 30% longer. That translates into better accuracy by the shooter. (The accuracy differences attributable to barrel length are negligible.)