I have both a GPS V and a GPS III. If you can scrounge up the money, the V is definitely worth it. The more detailed screen, much more detailed maps, and autoroute functionality are all great. I frequently use it to mindlessly guide me to where I need to go, and it works wonderfully.

The III, III+, and V are all the exact same size, and I think very hand-friendly. They're not quite as tiny as the eMap or some of the other smaller units, but they're still very portable.

However, if your primary interest is geocaching (which I've done a bit of), you really don't need the map functionality at all. In fact, all you need is to be able to enter the coordinates and then have the GPS tell you how far and in what direction. Practically any GPS will do this, so you could even pick up a simple older unit for $50 or so, and not ruin your geocaching experience one bit.

So, geocaching, it doesn't matter, everyday GPS use, get the V.

Alex