I use a Vibra-Probe and my wife uses a Bullseye ... in playing around with both of them:
Vibra-Probe: waterproof, signals by vibration only, bulkier, seems to be more sturdy, once turned on you don't have to keep pushing a button
Bullseye: lighter, have to hold a switch when in use, signals by sound or vibration, picks up a target at not quiet twice the distance of a Vibra-Probe
speaking as folks very new to detecting, we find using a pin pointer to be extremely helpful ... as noted above, in soils that cause a coin to discolor they make finding one much easier
Jim