Basically you need to figure out which model is best for you. If you intend to throw the gun in a pocket holster or a coat pocket, your best bet would be the 649. My personal preference would be the 60 because it is slightly smaller, lighter and I just like the external hammer. My personal choice would be a lightly used (95 + % condition) 60-7 made in the mid 1990's as I truly believe it is the best version of the M60 Smith ever made.
As far as the .357 in a J frame is concerned, I think you will soon find that the J frame while capable of shooting the cartridge, is not really practical. Too much muzzle blast, recoil, and slow follow up shots to deal with. The actual muzzle velocity of a 357 magnum (Rem, Win, Fed) out of a 2" tube is not a lot more than the 158 gr. BUFFALO BORE +P LSWCHP that is much more manageable! I have personally chronographed the BB +P's form my 2" Chief's and it clocks a true 1040 fps and 361 foot pounds of energy. The much more difficult to handle 357's won't give you much more, and the new versions of the Chief's Special are larger and heavier guns than the older 60-s.
If you are truly interested in carrying a .357 Magnum, I would suggest stepping up to an older Model 65 3" bbl. which is heavier, larger, and will give you better velocities and less muzzle flash than the 2" light weight gun. At least you could justify the cartridge in that gun.
Just one man's opinion, but you asked.
Chief38