It is better still if the unit can receive all channels at once as it is far quicker to acquire and maintain lock, and not multiplex them. It is rare to receive all 12 satellites at once but simultaneously looking at 6 is better than multiplexing 6 satellites. Patch aerials may be somewhat better for reception as they pick up signals from directly over head to 10 degrees above the horizon. Quad antennas can pick up satellites close to the horizon, but do have trouble directly overhead. This means that the patch would be better down valleys.
Some units allow the addition of an external aerial to increase reception.
As owner and user of a GPS, I thought this article on Global positioning systems was rather good. Thank's to C.Farley for supplying the article. They have been available for many years, but it is only recently that they have become small and affordable enough to use in mountaineering applications. Most weigh less than a pound. How it works The United States Department of Defence has placed 24 GPS satellites into Earth's orbit.