For hunting purposes, and fishing, too, any unit would probably do. Fish are particular and maybe 15 feet makes a difference. I would consider not just the readout, but how the unit interfaces with the computer back home or a laptop in the field. Can you load a day's worth of waypoints onto a screen map that is good enough to be useful? Is it easy to connect the two and is the software a snap to use? Some units are well-supported this way, and some are next to useless. Garmin, Magellan have top models with all the bells and whistles. Or a cheap unit will have the basic readout, possibly a simple map display, and not much more. Then, too, you need to look at what is running on the computer and whether the GPS will interface to that particular program without a lot of hacking.
Garmin, and Magellan are the compatible ones. Probably the simpler the better, I can't even get him to answer the cell phone.