Bell is pretty bad, of course, but none are good. The S76 seat becomes torture after a few hours. There is never enough thigh support, and the angle of the seat makes my back hurt. I end up with an aching back in every model I've ever flown. Fortunately, it has never been permanent, and after almost 40 years my back is still in decent shape for the shape it's in. I've never had any permanent pain, just the ache that goes away after getting out of that &%$#*& seat. The worst I ever sat in was the TH13 (Bell 47), but the 206BII wasn't far behind. The designers do all the design work on getting everything working, and then realize they have to put in seats for the pilot(s) and passengers, so they seem like an afterthought, not something actually ergonomically designed, or even designed at all. A cheap car has seats that are comfortable for hours on end, and which don't get leaked on in rain. Multimillion dollar helicopters have crap for seats, and leak gallons of water. Go figure.
One thing that has helped me immensely is a Relax-o-Back seat. It looks like a farm tractor seat, and I get kidded about my John Deere seat, but it's really very comfortable, and lets me endure for much longer than I could without it. Having a space for the tailbone makes all the difference, IMO. It's a cheap, and easy-to-carry, solution.