In the cooler months (when I can layer up for concealment), I carry a Smith 686 3" bbl. In it, is Speer's 158 grain GDHP's. I like heavy bullets.
Here's my chronograph data for four common factory defense offerings. Guns used were all Smith 686's. One 3"; one 4"; one 8-3/8". All data is from 10-shot averages. Yes, it was an expensive day at the range
Federal 130gn Hydra-Shok Low Recoil:
1356 f/s 3"
1430 f/s 4"
1538 f/s 8"
Advertised as "low recoil," but there's nothing low recoil about these. They are hot.
Speer 135gn GDHP Short Barrel:
1153 f/s 3"
1223 f/s 4"
1215 f/s 8"
These are an intentionally "de-duned" product from Speer, designed for 5-shot snubbies. The bullet sports a huge hollow cavity that is clearly designed to open up at low velocities. They obviously pack a smaller charge of faster propellant (hence, the lower reading with the 8" bbl) than most other offerings. Recoil is very manageable through my L-frames; but are probably still a handful in a snubby.
Speer 125gn GDHP:
1346 f/s 3"
1460 f/s 4"
1560 f/s 8"
These are hot, big, loud, powerful rounds. It would seem they wanted their 125's to be their flagship defense loading for 357 Magnum. If you're in the lighter bullet camp, these are probably the ones to get.
Speer 158gn GDHP:
1078 f/s 3"
1153 f/s 4"
1190 f/s 8"
This is the round I carry in my 3". With Speer's exceptional bullet design, I have complete confidence in their terminal ballistics at 1078 f/s. Recoil, although pronounced in its own right, is more rolling and less sharp than the lighter offerings. Lower flash, less recoil, and a heavier bullet. My personal choice.
Hope this information is useful.