Just my opinion, but the original M17's (and 4" M18's) are fantastic guns. The 617's (actually an L Frame) is no wheres near as good IMHO. I have a few of them and they are trouble free and tons of fun!
The 617's are still K Frame revolvers! They have the heavy lug barrel profile of the L frame. I have put thousands upon thousands of rounds through my 617 no dash, 617-6 ten shot and 17-8 and all have been trouble free. The 617 no dash out shoots my 1950's K-22s, My 17-3 and 17-4.
I do admit, the blue on the 17-3 and 17-4 is absolutely beautiful and is not matched by any S&W made recently.