IMO the 4" M29 is the definitive S&W N frame. Mine is absolutely great, and is a recent manufacture 29-10. If I knew then what I know now, I would likely do what others are recommeding and get a shooter grade 29-3. If I was going to own only one N frame, it would be a 4" M29.
These days I carry a 3" 629 every day AIWB, but before that carried my 4" M29 OWB and sometimes AIWB though it's a bit long for comfort. They are heavy, especially OWB, but a good belt helps quite a bit, and frankly I've gotten very used to carrying them. In the pics below I could also have carried my 6" M629, though I'd be more worried about the barrel sticking out if I raised my arms.
As far as recoil, the 6" does recoil a bit less, but what makes the big difference is the grip. Because the 6" isn't a CCW, I leave big rubber grips on it. Those grips help far more with recoil than the extra 2" of barrel.