well, ive only ever driven my car on solid mounts, so i cant compare with/without,
but the solid bush sits on a tiny layer of poly, and should help reduce noise, and it looks neater afterwards, as the solid mounts leave a gap between the body, which the bush filled.

im not sure if you can still get the bush i used, it was part of the deflex rear beam bush, as it came in two bits


if you look at the solid mounts only a small center section touches the body, i wasnt to keen on all the rear weight sitting on such a small surface area, in fear it may crack the leg, so the bush spreads the load over a larger area aswell