Etrex 10,20x &30x
Each of the models come with a specific intent behind them, the eTrex 10 is designed to function as a basic GPS device, you can set up waypoints and some other basic functionality but it does not allow you load maps like the eTrex 20x which again comes with a couple of extra features along with all the eTrex 10 features. The eTrex 30x is the highest tier model for the eTrex family its offers a couple of additional extras again like the electronic compass, barometric altimeter and wireless functionality.
For all intents and purposes, the eTrex 20x is the best option out of three balancing price and features. The 10 suffers from the lack of TOPO maps making it a very niche product, the 30x while the most powerful is the most expensive and begs the question as to whether the additional features are worth it. If you need a basic reliable and pocket friendly gps to start up your adventure or survey business then etrex 10 is the perfect partner for you.