I found this via dejanews (google) and while some of the references are old (see Iridum) the explaination of the different types of orbit are very good... Pros and Cons are quite clear in the different types of orbit. It was written around Feb 2000.
Hope it helps...
[quote]When a satellite is launched, it may go into orbit at any height above the earth. There are generally 3 different classifications for satellite orbit heights, described below.
GEOS (Geosynchronous Earth Orbiting Satellite) - This type of orbit, also referred to as geostationary orbit, is when a satellite is launched to an altitude of precisely 22,300 miles above the Earth. At this altitude, the satellite orbits the Earth every 24 hours. Thus, to an observer stationed on the Earth, the satellite appears to be stationary. This is a tremendous advantage, as it allows complete 24 hour communication within its huge footprint (covering approximately 1/4 of the Earth). However, geosyncronous satellites are not ideal for voice circuit transmission. Due to their height above the it takes radio signals approximately .25 seconds to be transmitted to the satellite and reflected back down to Earth, depending on whether the signal is passed among satellites before it is transmitted back down to Earth. This delay is quite noticeable, and you may notice it when talking on international calls.
MEOS (Medium Earth Orbiting Satellite) - This type of orbit is within 6,000 - 12,000 miles above Earth. Approximately a dozen medium Earth orbiting satellites are necessary to provide continuous global coverage 24 hours a day. Several MEOS systems are now in development, most notably Bill Gates and Craig McCaw's Teledesic project, which will ultimately attempt to provide Internet access to all corners of the globe (all under Microsoft software, of course
LEOS (Low Earth Orbiting Satellite) - This type of orbit is generally within the 500 - 5,000 mile altitude range. Although the satellite footprint is greatly reduced, global coverage can be accomplished through a network of satellites, in which if an uplink is required to be transmitted to a location outside of the footprint, the transmission is passed from satellite to satellite until it reaches the satellite which has the location within its footprint. As there is no noticeable delay for signal transmission, low Earth orbiting satellites are becoming the preferable method of voice transmission, with numerous companies currently attempting to establish LEO satellite networks, most notably Motorola's Iridium project (see <a href="http://www.iridium.com
The person who wrote it sure seems to know his/her stuff..