From Henry Shires (Tarptent) ..
The solid interior is warmer and better for environments with blowing dust or cold winds. The mesh interior is better suited for warm/hot and humid environments
I guess you need to decide how often you will be exposed to dusty wind blown/cold wind conditions to warrant the solid interior. I know for me in the south-west, the mesh is fine; up north it may be an issue now and then but I suspect I will be okay with mesh 99% of the time.