I have had just the opposite experience with my S&W autos.
My first was a first generation 9mm, a 39-2. I loved that gun! I still kick myself for trading that one away. I fell for the hype over the supposed improvements of the 3rd gen models and bought a 4006.
The 39 had a much better trigger than the 4006. It was lighter (alloy frame) and fit my hand better with the curved backstrap, not to mention the fact that it had a thinner grip being a single stack.
I have taken the 4006 to a Smith 'smith to try to improve the trigger, and while he did improve it somewhat, the 39's is still better.
The design of the 3rd gen Smiths at least allows the grip to be thinner than the first and second generation model doublestacks, so at least it doesn't feel like I'm holding on to a 2x4 piece of lumber. I agree with Quantum about the Durlin factory grips of the 3rd gen being too slick. I have tried Hogue wood and Hogue rubber aftermarket grips, finally settling on the rubber version. While adding just a tad in width, they are much better for slip-resistance and soft enough to allow a better recoil attenuation. They even are slightly curved on the backstrap so that makes them fit better (for me). For those of us with smallish hands, I wish Smith would make a single stack .40, both full size and compact, and bring back a full-size single stack 9mm as well. Then I'd be a happy camper.
The weight factor of the all-stainless gun was my own fault. I thought the stainless frame would allow the gun to hold up better than the alloy frame. The alloy frame on my first 39 was getting rather beat up where the barrel lug slams into it on firing. With the greatly inceased power level of the .40 I was really concerned about that being worse. I suppose my first 39 just needed a new recoil spring.
As you might have guessed, I have gotten another 39. I had to look for several years before finding a good one at a good price. I still had to pay more for this new used one than I had paid for my original one bought new back in the mid '70s! Now to find a set of factory grips for it....