Go with a mounted antenna, not the magnet type. Low branches will take out magnet antennas. I have a firestik mounted to my rear tire carrier and has faired well with trees on the trail. Magnet type are also easier to steal, has happened to me before. I agree with AZ-Ted, a professional install is the best way to go to get the best out of the antenna's range, dependent upon placement of the antenna.
Linky