I have one of the older inserts and one of the newer. I really don't see much difference other than cosmetic. I don't think the mesh is different at all. It is very hard to avoid snagging the mesh! I mended mine on the older insert. You could tell I mended it, but I did it mainly to prevent the hole from getting bigger. I only put soft things like gloves and drying cloth in the mesh but I think it gets snagged when I stow in my car's trunk.
I never used the clip on the older insert. The newer one doesn't have the clip, just a large snap, which I also never use.
One change on the newer inserts that I do miss - inside the Zuca, the older insert had a mesh 'pocket' hanging down from the top. I didn't even realize it was there for a long time, but once I did, it was handy for storing small things, like handwarmer packets. The newer insert doesn't have this mesh pocket, and I keep looking for it!
I wonder if the fabric differs by insert design. I see no difference in fabric for either of my inserts. Hope that helps!