Hey there Sam, the models you reference are outstanding firearms, and I dare say they are the standard by which all others are judged today. The M686 spawned a whole new area in .357 revolvers, where Ruger followed with the GP and Colt with the King Cobra. The M686 was designed to allow for over 10,000 rounds of full power loads through it as the
"starting point". Many models are available, from 3" to 6" (today, previously you could get up to 8 3/8"). If you get a M686, you will not be dissapointed. As far as the M629, what can I say? It is the stainless version of the famous M29, and is as solid as they come. Others will say that there are stronger designs out there, notably the Ruger Redhawk, which is an outstanding piece, but if you stay within SAAMI spec's for loaded ammo, the M629 will last a very long time indeed. The DX has some extra features that the standard Classic does not have, most notably the removable front sight blade, which allows you to change the sight insert to match your use. Earlier, the DX pioneered the round butt, and had "extra" hand fitting of all the internals, but that has been dropped these days. The DX is a nice piece, and you will not be dissapointed if you get one. Any of the M629's will do you fine. If you get to sample the Performance Center versions of either, well let's just say you will be surprised and gratified with the nice workmanship. Enjoy. ......SmithNut