I use the Nuvi for Geocaching, and that's what I'd use the eTrex for as well. I'm not sure what eTrex I was looking at, though it was yellow. It cost about $100 if that helps.
I don't have a PDA, but honestly, I don't mind carrying a few sheets of paper with cache coordinates and descriptions. Should this factor into my decision?
Also, I forgot to ask: is it easy and simple to put coordinates into the eTrex?