I've been using the Garmin Etrex Legend. This unit has 8 mg of Ram. If you could go the extra 'mile' and reach for the Vista, you'll get 24 mg of ram. Both will work well. But you need to buy the "Topo" software as an extra. You load the software into your PC. Zoom in and pick the geographic areas that you plan on ridin in. Download the maps to your GPS. Get a RAM mount for your GPS. Make a modification to the top of the mount by drilling and putting in a bolt and nut to insure that the GPS won't pop out on your trail runs. The internals of the GPS allow you to save tracks. My bro and I have been doin' this since this summer and have been e-mailing the tracks to each other. This is so cool when you upload to the PC and you can 'see' the trails you've ridden. If you need more info, ping me. Happy Trails!
The E-Trex Series of GPS hold 10 Individual Tracks at a time. I had one single continuious track from New York, accross PA to Columbus, OH UP I77 Accross I 80 Back to NY and only used about 60% of my Tracks Ram. This was in my '02 Ranger not ATV. What I usually do is record 1 track from whereever I'm starting from to the destination of the Trail Head. Save & Name the track log, clear the track log and start when I'm riding a Quad. Depending upon different trails and how detailed you want to become you can then save as many times as you want.
Jury still out, I got mine recently and went for a larger unit then I expect any of you guys would want, a Garmin 176, as I will be using it for Copper Canyon trips on my ADV R, and on my VFR as well. I bought mine on eBay figuring it would get trashed anyway, and saved $200 or so over new. If your planning on running off the batteries, I would check out TouraTech site. They have some info, as the batteries tend to arc at the terminals, and on thumpers it can get pretty bad, and oxidize the terminals. The trick is to use dielectric grease between the battery and the terminal, some units if you tape the batteries really good, and place some foam under the terminals, something like a chunk from some ear plugs. This is said to help. You don't even want to know what the Touratech mounts cost, argh.
Found this guy on eBay vl1066 his prices on memory, adapters, cables, etc. seemed awful low, but I gave it a shot, and everything showed up as advertised. I knew the memory wasn't Garmin, but a knockoff, but to my surprise everything else was actual Garmin stuff.