Wolff will tell you - their springs aren't for every gun - or everyone. A 625 destined to fire moonclipped rounds needs to whack pretty hard as it has the added slop of moonclipped rounds to contend with, thus the stock OEM hammer spring is best, with the reduced one useable reliably only with Federal primers. The trigger return spring change affects both the DA and, slightly, the SA pull - but in a competition gun, it can slow down your trigger's return... again, in a 625 destined for competition, the OEM's are best.
My experience with a Ruger DA spring change was my .454 SRH - the same lockwork as the GP-100. With the heaviest replacement springs in the 'kit', I still experienced the most un-nerving sound... a click when I expected a .454 boom! Back to OEM's there. I also leave the OEM springs in my S&W 2" 10, 3" 65, and 2.5" 296 - they are CCW's or for home defense. They will remain 'stock' - and fed with only commercial ammo - for both legal reasons and assurance that they will 'work' reliably when needed. My other 'fun' and 'plinker' revolvers, except for my Redhawk and Ruger SA's, have Wolff springs.
The greatest improvement in a Ruger or an S&W can be had for just a little work. If you ask a decent 'smith what an action job does, he will tell you it replicates a lot of firing... so why not do it yourself? Seriously, blasting the gunk & dirt from a new or like-new S&W (or Ruger) , followed by some oil and a lot of dry-firing (1,000+ - use snap caps if you must.), and a reclean and light lube, and you, too, will have a 'decent' trigger! Seriously, try it - you will be amazed. The beauty is that the wear parts are 'wearing in' in the proper geometry - and in proper relation to each other. I do this before I fire a new Ruger or S&W - I liked my Redhawk so well after this that I never altered it's spring... the S&W's fun pieces all got a reduced power hammer spring, as I reload now... and use solely Federal primers. I have seven '01 or newer S&W's, all bought new, I've treated in that manner - with at least reduced power hammer springs - and they are super.
Another great Wolff spring... a 50% STIFFER spring for my Marlin Camp 45. It seems that Marlin used the same recoil components, and same mass bolt, in their neat 9mm and .45ACP carbines, despite the 50% greater momentum and KE of the basic .45ACP ball ammo... the result before the spring was often a cracked stock. I changed mine, a new safe-queen bought over a year ago, and have had no problems of any kind... and, I still have the original stock.
Stainz