I only use prime focus dishes as I prefer them especially as I have to brace them for typhoons. Offsets have one arm holding the lnb below the dish whereas prime focus has 3. I also prefer this as the arms can get hit by flying debris in high winds. Offsets look smaller but a 1.8m offset should give the same gain as prime focus.
Apart from that nothing to choose from excpet I have not seen a mesh offset dish only solids.