I don't mean to discount the argument - I'm just saying it's an issue of degrees. In other words, sickness will come on either boat if you're susceptible and the conditions are right. Then it simply becomes a question of:
1. Do you puke 2 times less on the older bluewater boat than on the newer production boat?
2. Does it take you 2 hours longer to start puking on the older bluewater boat than on the production boat?
So, I fully acknowledge that it's a factor. There is math involved. And I respect math.
But I certainly wouldn't want to sell my family on the notion that they'll be more "comfortable" (i.e. - not puke) on an older bluewater boat than they will be on our Hunter 40 in the same conditions. I just think the actual differences are marginal.
Again, I'll have to see when take our H40 out this spring.
With respect, I think you haven't sailed on a wide enough variety of boats to make that determination yet.
There's been quite a discussion among some friends of mine, about how seakindly a Hinckley SW42 was, during their race to Bermuda. These are guys that have been racing for 30 years on an incredible variety of boats.
Seakindlyness can be very important. Nausea and vomiting bring on fatigue, dehydration, and bad decision making. A ride that avoids or delays the onset of motion sickness, keeps the crew more rested, in better health, and making sound decisions.
I think the difference can be much more than marginal, between some designs and is well worth considering, if ocean sailing is the purpose of the boat.