The 617 is built on a SS K-frame, the same size as the Model 10, 64, & 67 now. They share a common gripframe - and resultant grips - with the L-frames, like the 620, 686, & 696, too. It's a comfortable 'plinker' size. It has the same lockwork as the L and N frames as well, including a smooth leaf hammer spring. There are easily made improvements to the lockwork in this size revolver. The front sight replacement with a HiViz was easily done - I could find said sight.
The 317 is an Al J-frame - smaller - and generally a 'pocketable' size (Unless it has a long barrel - like my 5" 63 below!). The smaller gripframe permits smaller grips, with larger grips just seemingly unavailable (The aftermarket squared Hogues on my 63 were the largest I could find.). The lockwork is particularly stout, due no doubt to the strong wound hammer spring and the shortened geometry of said lockwork (It can be improved - just not as much as the K-frame!). I haven't found a HiViz type front sight for mine yet.
There is a new 3" 63 due out this month - with a HiViz sight, a la the current 317K. As it is essentially a SS 317, it will share the stout DA pull of the 317, too. Even S&W recognizes the limitations on improving the 63 & 317 DA pull, as they only offer an $85 minor 'trigger job' for them. They err on keeping a stiffer hammer spring - insuring your revolver will go 'Bang!' with all rimfire ammo.
I have looked at the 317K many times... just couldn't convince myself I needed one that badly - even a recent $375 LN used one at the pusher's. I jumped on the LNIB 5" 63 from a friend's estate. I have improved it enough to make it fun to shoot, DA or SA. Both the current 317's and 63 are 8-shooters - a DS-10 8-shot speedloader and loading plate make the 5" 63 a fun plinker - not as much so as my 4" 617 X10, but getting closer. Maybe it just needs a HiViz style front sight? I hope this helps.
Stainz