That would be a good reason!
On the lead bullets . . . if you can get a few .357 - I wonder if you'd have the tumbling problem? You don't mention any leading problems so the .356 must be going down the pipe O.K. without leaving any behind? In most cases, tumbling is caused by poor bullet to bore fit. If I'm interpreting correctly . . . stepping up the powder and thus the FPS took care of that?
As you already know, every handgun is different and likes different things. In my SR9, I've been using the 120 is gr. RN from the Lyman 358-242 "as dropped" - which is right around .358. All depends on what I'm casting from as I only use "range lead" and that can vary from batch to bat. If over .358 I size down to .358. But . . . that's in my SR9. On cast (lead) I like to be .002 over bore size if the cartridge will chamber correctly. All I load is cast in pistol and rifle - I haven't a clue on the plated once.
I can't answer your question on the spring stiffness. When I first got my SR9, the spring was pretty stiff and it was on the hard side to rack the slide. That seems to have gotten better over time and rounds through her. Plus, I'm pretty much a revolver guy and some excellent training I got in some classes from "pros" (LEO, former Spec. Ops. Military and S.W.A.T. members who were the instructors) helped me greatly in a lot of areas in using a semi-auto - including "racking", hold, etc. - I always learn something new and i enjoy taking SD classes whenever I can.
When I was looking, I remember that I didn't care for the shorter grip on the Src - but that's just my hands I think. Had I gotten the SR9c, I'm sure that I would have adapted.
I have no problems buying vintage/used revolvers. I have had a number of semi-autos - only two were "used". One was a Colt 1911A1 that was given to me in 1964 - brought back by a Navy Pilot after WWII. It was "mint' with the original holster, clips, belt, mags., etc. I ended up selling it as it was just too nice - a collector bought it and I doubt that it had more than a couple hundred rounds though it. The other was a Bersa Thunder .380 CC - nice shooter and reliable but the previous owner had done "trigger work" on it. After the first DA shot, when the gun was in SA mode the trigger pull was so light that I got a number of double shots without intending to at the range. Not good for a SD piece - so I quickly returned it.
I have a complex when it comes to buying "used" semi-autos. I always wonder if the "owner didn't like it" or if there was a reliability issue? The one thing about the Ruger . . . if you bought the SR9c and there was an "issue" with it - Ruger is good about customer service and taking care of it.
Good luck whichever way you go and let us know what you end up with!