I have topo maps for my Magellan. Other than being an older model and not having a touch screen it work great. In 5 years I've lost reception on it 3 times, and even then only briefly. Has NEVER locked up on me.
My Garmin Nuvi350 has been a nightmare. I'm on my third unit, first two were replaced under warrenty. The 2nd unit arrieved broke.
Coast me over $100 in shipping and duty fees. Hopefully this one is good as the week it arrieved the warrenty ran out.
Most GPSs don't work well for on and off road navigation, they are usually geared to one or the other(my Nuvi350 has no provisons for downloading topo maps or saving waypoints). Magellan makes a cross over unit that is supposed to do both but when I looked at it it was brand new to the market(1 year ago) and it still had some issues to work out.
I've owned one Garmin(Nuvi350) and 3 Magellan's. Thought I tr the Garmin as I do like the ease of the Nuvi for street navigation, just wish it was as reliable as my Magellan. This fall I'll be upgrading my off road GPS again and I don't know what to get. All my friends have Garmins so it would be nice to share files with them but the also have had problems with their units freezing while on the trail and losing signal whereas my Magellan was so rock steady I'll have a hard time moving away from it. Especially after my Nuvi experience!
Some things to look for no matter what you get. Removable storage media such as an SD card, then you can upgrade to whatever size memory you want, USB cable interface(I think they all do now anyway), battery life and type, personally I like something that takes regular AAs. Easy to find and carry spares. Waterproof isn't needed unless you like fording deep water. Get a good mount, something that bolts/screws in. Suction cups don't cut it when bouncing on the trail. GER THE LARGEST TOUCH SCREEN POSSIBLE. Bigger IS better.
Go to GPS central and try different units out. Each time I have bought a GPS I've done research on the net, walked into the store intent on buying one unit but after playing with them and comparable units I've ended up buying a completly different unit.