It is a generalization to say a 8' solid performs like a 10' mesh. Too many factors come into play.
At 4GHz a mesh, perforation or solid sheet will all appear as a similar solid RF reflective surface.
The forming of the parabola and mechanical support accuracy are the most important factors for reflector efficiency.
A solid one piece spun or hydro formed parabola typically has the best performance. A quality build one piece composite/fiberglass reflector with carefully laid reflective material also performs very well.
Panel type reflector performance is based on the accuracy of the formed panels. Commercial panel reflectors are well reinforced and constructed to form a very accurate parabola. They usually age very well and a 30 year old reflector often performs as well as new. Consumer grade reflectors ranged from quality to crap and from small quantity regional manufacturers to mass nationally produced units.
The main weakness of many mesh panel dishes is the way the mesh is formed. Often, flat mesh panels are assembled onto frames to form the reflector. These panels roughly form an inefficient parabola. Other mesh reflectors used formed panels preassembled onto the panel frames, yielding an efficient and a more accurate parabola.
With all of this said, I would take a 8' one piece perforated spun aluminum reflector over any composite/fiberglass or panel 10' reflector any day of the week! Give me a spun aluminum 10 or 12 foot reflector and I would be in 7th heaven!