I've shot an old six shot four inch model 63, I wasn't impressed with either the trigger pull or the accuracy. Ditto the Taurus copy, which gave patterns rather than groups.
I don't like the 617 - the underlugged 6 inch barrel does not balance for me, although it is very accurate. As you are used to the 686 this may not be an issue for you.
I do love the model 18 - four inch skinny barrel gives perfect balance and pointing. It's currently my favourite hand gun, but this is probably partially due to the fact that it is my newest gun.
I sold my Single Six, MK II & 22-45 to fund the 617 for my dad. I still regret selling the Single Six some five years later.
I found the accuracy with .22lr to be no worse than the 617 & for a small game hunting firearm there is no need to rapidly reload. It's squirrels and rabbits you are looking at, not human waves in Mogadishu.
I also found the slow load and reload cycle to be quite calming at the range, There was no ability to shoot rapidly, so every shot was made to count. The single six pointed well in my hands which is always a plus. Last, for small game hunting the .22 magnum cylinder will give you that extra bit of energy to ensure clean kills, something every ethical hunter should keep in mind.
Summary: Get the Single Six as your hunting handgun. If you still use a 686 as your main SD gun, then consider a four inch 617 as a complementary training firearm. It will probably pay for itself in saved ammo costs