i reccomend a garmin 72 ,can be baught and setup with mount and remote power for about $150 and change from ebay.most handhelds are about the same till you add mapping and color.the screen on the 72 is a tad bigger than most.eagle has a nice gps,ff combo for $200.00. tracback is nice feature for working a structure line too.
We have an older garmin E-Trex handheld. I don't really like it because it is not simple to drop a waypoint. IMHO, one of the most important aspects of the GPS should be a 1 touch drop of a waypoint, so while you are trolling, you can mark a fish easily and quickly. On this little handheld you have to scroll through menus, choose a point, name it, drop it.
But what can I expect, it was not made for fishing.