I have a Magellan 315 and a Garmin 12XL
I use the 315 for preference, half as many batteries and they last longer. Also have a flexi mount for it which suckers on to the windscreen and puts it exactly where I want it.
12XL takes a remote antenna, 315 will not. Never had any loss of signal in the Luscombe so not a problem.
I have the DataSend Aviation and DataSend Europe CD's. They enable you to upload cities/towns/villages and ad's which is very useful and makes it dead easy to find your position on the chart relevant to ground features shown on the GPS. Cable will also supply power to the unit via cigarette lighter socket.
Capacity to hold plenty of routes and user waypoints, far more than I need.
Never any problem with it and can thoroughly recommend it.
Mike