What do you mean as best? Longest battery life? Fastest satellite acquisition? Most accurate? Most features?
Note that accuracy is controlled by the controller of the GPS satellites, usually a country's military service. Weather and terrain can also affect the accuracy. Steel buildings, granite mountains, and dense vegetation can also affect the radio signals from the satellites.
Almost all have the same internal circuitry.
Many handheld GPS units track more data than the camera specific units.
Do you want your GPS to do more then tag your images?
I use the Garmin GPSMap 60CSx for land and water navigation as well as for tagging images.
You might also want to read the manual for the GPS you are interested in and see what data it collects and what data your camera can record. For example, Direction or heading can only be detected by many GPS units only if they are level to the horizon and orientated in same direction as the camera lens.