Typically, fixed focal length macro lenses have a magnification of 1x, so the subject is the same size at the sensor. Focal lengths tend to be relatively shorter, with the longer ones getting expensive fast, but lenses have relatively big apertures. They can be used like any other normal fixed focal length lens.
Telephoto zoom macro lenses tend to have lower magnification, smaller apertures but longer focal lengths. The subject size typically wont get as big as it could with a fixed focal length one, but the longer focal length allows you to be much further away from the subject. This is particularly useful for subjects that tend to run away if you get close.
When deciding on the lens, standard considerations apply with respect to trading off focal lengths and motion blur risk, aperture settings for depth of field vs brightness vs shutter etc...
Personally I use both (300mm tele zoom and 90mm prime) depending on the situation. If I have to pick one for walkabout, then the zoom is much more versatile.
_________________Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.