Check out the full review of the Garmin eTrex 20 and the Handheld GPS Review where we compare the top GPS devices.
The Garmin eTrex 30 has been replaced by the eTrex 30x, which also retails for $300. The 30x now features an updated screen with a higher resolution (240 x 320 pixels versus 176 x 220) and now has 3.7gb of memory instead of 1.7gb. With the 30x, you'll also score a subscription to Birdseye Satellite Imagery.
See below for a side-by-side comparison, with the eTrex 30x shown on the left and the eTrex 30 pictured on the right.
Garmin eTrex 10, $110. The main differences are that the eTrex 10 does not have a color display or expandable memory and costs less. The dimensions, weight, and battery life are the same.
The Garmin eTrex 20, $200, is the best value. This is our favorite GPS for backpacking because it's the lightest GPS we've tested (up to 4.3 oz lighter than others) and it has great battery life.