Geo-synchronous orbits are at 22,500 miles in altitude, which is over five Earth radii. The time delay for the signal to travel to the satellite and back is about 0.3 sec and is noticeable. Polar orbits are much lower, so there is no delay. Polar orbit satellites travel around the Earth anywhere from 1-12 hrs, and require many satellites for complete coverage. Satellite communications must be UHF and higher in order to penetrate the ionosphere, and are commonly in the SHF range.
Bandwidths are generally in the GHz range.
Furthermore, circular polarization is predominately used since it is difficult to properly orient the receiving antenna to match the satellite antenna if linear polarization where used.