It's odd how they pick and choose the chassis they use. You are 100% correct on the 24,000# chassis with the 34'er, and on the 36' 1" they go to a 26,000# chassis - yet on the 36'5" and 37' 6" they drop back to a 24,000# chassis. Why?
On all of Newmars Canyon Stars they use the 26,000# chassis, regardless of length. On the Baystars they primarily use the 22,000# chassis, bumping up to the 24,000# on the 35' 11" models.
Winnebago seems to use a different chassis for every length on the Adventurer, and it seems to be hard to find anything heavier than a 22,000# after that.
My point is, like always, everyone needs to research the MH they're considering first and pick what works for them. IMO to say Tiffin has better bones is painting with too broad of a brush, as it varies between competitive models and floorplans.