I have nothing but great things to say about my Garmin Oregon 450t. If you watch you can get it on sale for a pretty good price, but it is more expensive than the eTrex.
Having said that, I had actually originally purchased the new eTrex 30 before I got my Oregon. A backorder issue allowed me to change to the Oregon when it went on sale. I previously had an eTrex Vista HCx and was very pleased. I would not hesitate on either the eTrex 20 or 30 if you just want to add the hunting GPS maps. My only caution is that the eTrex 20 does not have an electronic compass. I would not purchase a GPS for hunting without one, but that is just because the way I use the device it's much more efficient than taking along a compass. You could definitely make it work without one though.