I own three of the ones on your list and I have shot the fourth.
If you are going to carry it, the SP101, no questions. I routinely shoot full power .357's (not max/heavy loads) out of it and recoils is similar to .38 SPL's in an AirWeight. The trigger is most excellent, but it has had, according to the previous owner, some smith work done. It might be my favorite revolver... nah, that's probably my 4" Redhawk.
My 19-3 has the best trigger of any handgun I've owned. (I have the target hammer/trigger on mine.) I have occasional light strikes. This gun is too large for me to carry. It gets used mostly for teaching in my pistol classes. Strange that it is a .38 SPL... are you sure?
A 2-3/4" Speed Six is very high on my desireable list, but I own a 4" Service Six. The gun is near 100% and no trigger work has been done. I would like to find a local trade, but I've starting to give up hope. If I could only have one .357 Mag I would probably want a 4" Security Six with a trigger job. The lines and looks just don't get any better, IMO. I got a good deal on it and always wanted one, but it's not "exactly" what I want.
Newly manufactured GP-100's have better triggers that new Smiths or my Service Six. It is a large gun, and if range shooting or hunting is your goal than that would be my choice, but I'd probably go with a 6".