i just bought a garmin gps V. here is what i found on my research.
For general hunting and such all of the available systems will do the job. If ducks are his thing look strongly into something water tight. I prefer te garmin stuff as it just has a better "feel" to me. Keep in mind you will have to buy extra software <100.00+> if you expect detailed maps of any area. Memory size is not a big deal if you only need 1 or 2 detailed areas mapped. If you want to detail map more than 1 county look for a good bit of memory. Memory capicity adds a good bit to price.

hope this helps.
mike