Compared to standard 625s S&W no longer carries, the JM version has an interchangeable front sight, JM grips, full underlug, and a serrated trigger. The serrated trigger is forged, while the hammer is MIM, and flash-chrome treated to match the trigger.
S&W currently offers a 625 from their Performance Center. This 625PC also has an interchangeable front sight, but has a partial underlug, shorter cylinder, and psychedelic JM grips. And AFAIK, PC revolvers are also supposed to use forged (rather than MIM) innards.