Looking for opinions on GPS options for MTB'ing

Unless you always ride a handful of routes with which you're completely familiar, one suggestion I'd make would be to think of getting a mapping model. One huge benefit in having a GPS receiver on your bike is the convenience it provides in confidently navigating a route that's completely new to you. Even if it's not something in the forefront of your mind right now, it could still be something you could naturally grow into pretty quickly once you start using the GPS.

And a couple of quick comments about using a smartphone/PDA as a GPS while biking. While this seems to make good sense at first, it's far from ideal in my opinion.

• Picture your smartphone flying off its mount on your handlebar when you crash. Would you rather watch your smartphone land 20 feet away from your endo, or a ruggedized GPS that you can simply snap back on? (If you say you never crash, fair enough.)
• Even if you don't crash, would you rather be subjecting a waterproof dedicated GPS receiver to the trail dust and water or mud splatter, or a dainty smartphone with lots of headphone, speaker, and USB port orifices?
• Most smartphones don't have enough battery capacity to stay on for more than five or six hours. Considering you might not be at full battery charge at the start of your ride, it might not be able to get you through your ride, or leave you enough juice for the rest of your day even if it does. GPS receivers usually have a battery life of 20 hours or more.
• GPS functionality is almost an afterthought on most smartphones and their antenna sensitivity is anemic compared to any dedicated GPS receiver. And if you frequently ride under significant tree cover, you might as well forget about either GPS track accuracy or using a smartphone as a GPS receiver.
• All smartphones are touchscreen devices, whereas most "serious" outdoor GPS receivers use physical buttons. If you ride wearing gloves like many riders, using the controls of your smartphone without taking your gloves off could range from impossible (if it's a capacitive touchscreen) to frustrating (if it's a resistive touchscreen).

Some suggestions:

If you ever want to actually measure altitude or the total ascent on your rides, you want to get the ones with a Barometric altimeter. (Edge 500, 705, 305, eTrex Vista HCx, GPSMAP 60CSx, GPSMAP 62, ...) Otherwise, your altitude will vary all over.

If you go on long bike trips (>6 hours), get one with batteries that can be replaced such as by normal AAs. (eTrex Vista Cx, GPSMAP 62, ...)

I don't recommend the newer Dakota and Oregon GPS becasue the screens are too hard to read in the sun. The others mentioned above are great in full sun light.

The eTrex VistaCx is costs less than the Edge 305, has a better screen, replaceable batteries, more features, more customizable user screens, color mapping, barometric altimeter, compass, mapping, removable memory, more rugged .... better in every way except perhaps a touch bigger.

I used to own a Vista and loved it. But I finally went to the larger screen of the GPSMAP 60CSx, one of the most popular GPS units. The eTrex Vista HCx is rugged little unit fully stocked with every feature available at a great price. I don't get why it doesn't sell better.

I guess the Edge is just a little smaller and slimmer? The Edge does have some racing features (lap times, racing against a virtual rider,..) not found on the other GPS units.