The Model 25-2 is the 1955 target revolver for bullseye shooters. Originally had a 6 1/2" bull barrel. S&W later shortened to 6." Blued with pinned barrel, wide target hammer and trigger. It replaced the Model 1950, which had a lighter barrel and didn't find favor with bullseye shooters. I had my barrel cut to 5" and the trigger switched to a narrow, smooth trigger, and had the Performance Center do an action job on it. I then switched the mainspring for a Wolff spring.
The 625 is stainless with a lugged barrel, originally 5". Heavier than my 25-2. It was intended for pin shooters, the extra muzzle weight helping to reduce muzzle flip. It was intended to be a limited edition model, but became popular enough with IDPA, IPSC, pin shooters and general revolver shooters who liked a .45 ACP revolver that it is still in the line-up (after a brief lapse). With IDPA now requiring a 4" barrel for revolver, S&W has made it with a 4" barrel just for this group. I haven't used the 625 but I am thinking of getting one just for fun.