I went 642 no lock.
Have seen 442s w cracked frames, two of em and neither shot very much.
Interestingly, both were nickel.
If it cracks have Smith replace.
As for the finish..........if it gets to looking really nasty, have it cerkoted.
Its a tool, aint really worried about the looks.
Carry rigs get finish damaged.
642 got a Wilson spring kit and strut edges smoothed. Polished rebound slide.
After all that it feels the same to me.
Im losing my ability to feel subtle changes.
Guess that goes along w the ol ladys cooking tasting better these days LOL