GPS units

I think the basic purpose of a GPS is to navigate towards waypoints that you've either collected yourself, or which has been uploaded from a computer. The same goes for tracks. You can get very affordable models that do this just fine. All the fancier stuff is in addition. For more meaningful navigation add a topographic base map (one which you can load onto your computer too - this allows you to plan your route beforehand too, even if you don't have any real GPS data).

The newer models have some funky stuff, nice touch screens, 3D map capability (Berg maps have yet to catch up), topographic shading etc etc. But I've been using a Garmin Legend C for several years and will stick to it until it breaks, or until the fancier 3D maps become more meaningful and useful for the Berg and other places. I'm not sure if they still sell Garmin Vista HCx's but that one always had good marks in my books. But if you do go for a simpler model, I can't say for sure if you'll wish you had something better within a few years..I'm not sure how fast map technology is going to change. That's something you may want to run by a knowledgeable sales consultant.

There is a better way to using a needle on a leaf in the Berg these days: if you see smugglers, and they are carrying bags, then they are heading East. If empty bags, then they are heading West.

I don't know any of those GPS models. What matters to me in addition to the normal functions is being able to send and receive data to a computer, and being able to load IMG files / maps to the unit from a computer. If that is missing then the usefulness of your unit is more limited.