Interesting topic and it comes down to: money; features; use and what you like. You need to set a budget because GPS unit sell from $100 and the sky is the limit. If you want to use it for, so having a GPS unit that works on the road for navigation and able to record track or do you need a hand held that can be used hiking and offroad which does record tracks. This gets down to, do you want map (topographic) display or a basic (cost options) which include your features. Personal feel will come into it.
Recommend to look at other peoples setup and ask questions. In my case I have 2 GPS units. Garmin GPS60 (basic display) which has been great and does everything I need for offroad mapping as I capture the tracks and download into my computer. The other GPS is a TomTom navigator which in itself doesn't do offroad at all but loading a program call TTMaps (free s/w) onto my memory card and booting from that gives me offroad navigation and track recording but comes with a cost of purchasing maps that are 25,000:1.
Each system has good points and bad but visual GPS with maps I am starting to like more but I will still be using my Garmin with the external antenna gives great signal when driving through areas that has weak signals for the GPS