Maxer,
S&W has changed several things about the guns in recent years.
Many people don't trust MIM parts, many people do. For those who don't, a non-MIM gun would be worth a little more.
The frame-mounted firing pin is stated by S&W to be a stronger system, you'd have to ask either them or one of the more knowledeable posters here to explain how.
As far as the trigger pulls go, my info is that S&W has made some other changes to accommodate the MIM parts. The headspace has been opened up on current guns, as I understand it, to help meet California drop test requirements, and the current MIM firing pins are shorter. At least some current MIM hammers are hollowed on both sides, which makes them slightly lighter. Increased headspace, shorter firing pin, and lighter hammers would seem to require a stronger mainspring for positive ignition. The mainspring seat location has been moved slightly to increase the tension, and the result is a harder double-action trigger pull. Two recent brand new N-Frames I've had here had 12.5 & 12.25 pound DA triggers, and that's much heavier than a properly set up Smith should have, in my opinion.
The frame-mounted pin in itself would not affect trigger pull, but in conjunction with other changes it seems to have.
I don't know the transition dates or how many guns were involved in the transition, but S&W went to the frame pin first, then a year or three later went to MIM hammers & triggers. I have a three-inch Model 60 .357 Mag that has the frame pin, but forged parts. I'm not aware of S&W ever making any regular hammers with firing pins out of MIM, but I suppose it's possible.
Somebody else here might know.
I'm not trying to talk you out of the gun in any way, just answering your questions.
Good luck.
Denis