I know quite a few sledders will talk about how fast they were able to get their sleds going and they often qualify their speed by saying it was the speed achieved by their GPS unit.

As for myself in the car I have noticed that sometimes (in fact oftentimes) the speed registered on the speedometer is off a bit from the speed shown on the GPSr.

Call me bored or just plain curious, but in your opinion what is more accurate most often (recognizing that if you have an EPE reading of 360 it may not be all that accurate and that snowmobiles may have some track spin giving a false speed reading for example) -- speedometers or GPSrs?