My husband and I have been geocaching on and off for five years.
We have a Garmin eTrex (green) - have had it and loved it for about 6 years.
We "upgraded" to a delorom Earthmate - I hate it and can't figure it out - I RTFMed and read online - still can't use it as well.
I love the Garmin - just got my mom-in-law the newest high sensitivity one and she loves it too.
Of the two links I would go with http://www.rei.com/product/761620
(Garmin eTrex Venture HC GPS Receiver) because of the front joy-stick. Yeah it sounds silly - but previously my mom-in-law had the other one in your list, and without the silly joystick it wasn't as easy to use.
I'm assuming you are using this on the trail/geocaching and not walking around in town or driving.