Here's a link from NACHI comparing OSB to Plywood. Not TT specific, but fairly straightforward.
http://www.nachi.org/osb-plywood.htmIMHO, floor bracing dimensions, placement, thickness, etc has as much or more of an impact on floor stability as osb/plywood.
For example, our Starcraft has a soft spot near the entrance. When I check underneath, there isn't any water damage or issues, but the spot is directly over the fresh water tank, which means there aren't any flor braces there. It's barely noticeable, but I was 'inspecting' when I first noticced it.
I may add a brace there some day. I've read about some dealers adding a brace over the tanks in some models of RVs to strengthen floors, and IIRC some actually called for braces to be there but were omitted.
Water is definitely the enemy, osb/plywood/etc. Plywood wicks water from the edges readily, osb stay wet longer, plywood is more likely to return to original dimensions when dried than osb, plywood has more voids than osb, etc.
I do agree with those who say that 'Ultralight' does not necessarily mean 'Cheaply built' but in some cases it does.
