The unit I use is a *Garmin Etrec Vista C which is a model now seven years old.
The software that came with it (*MapSource) is pretty good and allows you to send waypoints either way - GPS unit to PC/Laptop and vice-versa.
This de-clutters all the waypoints on the unit allowing you to transfer just the waypoints for that days detecting.
A really useful feature is the ability to overlay your waypoints directly onto Google earth. This was used to good effect whilst hunting for Adders recently.
I only mark (waypoint) findspots as these are the critical points required. The tracking is only used on mountain bike rides to aid direction.
Crop marks are also marked with waypoints as when you are stood in the field itself, the field doesn't usually look like it did on Google earth!
The accuracy of my GPS unit is hovering around the 5 meter zone. Some newer models offer accuracy down to 2 - 3 meters using a mixture of the American GPS system and the later Russian equivalent; GLONASS.
Of course there are also GPS apps for smartphones if you have both smartphone and the data allowance to support it.
Whatever you use, it's certainly better than trying to remember a point on a Google earth image!
* Other brands of GPS equipment and software are freely available.