I like the concealed hammer of the 351C for CC, but the 351PD has a nicer grip - and was all I could find locally this January - so I bought mine for what I thought was $599, as the trigger guard string tag stated. The LGS owner rang it up as $629 + s/t, which I didn't notice due to the CC purchase - and the madness that was early January in a gunstore. It had to go back to S&W for a new cylinder & ejector, but I was happily shooting it by month's end - and carrying it, too. The slick wood grip doesn't print or stick, and whether from a 642-sized Mika pocket holster or a suede leather pocket holster, rapid draw and fire proved the hammer to be a non-issue. The wood grip is small in my medium+ sized hands, but easily & efficiently 'grabbed', ie, no fidgeting, and the low recoil is no problem. That grip would be miserable in my 632 Pro with real .327 Fed Magnums, however (That's why it sports the larger wooden '60 Pro' grips.). The 351PD is for pocket carry - and a true 'emergency' - it doesn't have to be a 'comfortable' plinker - I have a 4" 651 for that! I'd get the 351PD, given the choice.
As to DA trigger improvement... S&W offers an $85 'clean up' - no spring changes. There is a reason for that - the Magnum rimfire primer needs a significant 'hit' to fire reliably. My LNIB 651 got lighter Wolff springs initially - and ftf's. Back went the full strength hammer coil. Enter my 351PD... I did nothing but flood it's innards free of manufacturing crud, leaving little RemOil aerosol within it. It broke in nicely - actually, very equivalent to the broken-in 651. It seems stiffer than it really is due to the lite weight (10.8 oz) of the revolver - the muzzle seemingly wanders as you pull the DA trigger. Still, it is 'doable' for my wife and myself and easy follow-ups, due to the lite recoil, permit all seven rounds (Hornady 45gr FTX Critical Defense) to be put in the COM of a bg target at 7yd in seconds - good enough for SD - the bg will eventually notice those seven new exsanguination ports you've added...
Stainz
PS I still carry seven rounds in a screw cap poly bottle as a 'slow' reload, despite having bought a Speed Beez 351-7 speedloader and 4 x 7 loading block - great range aids, however.