Originally Posted by
mibike
For your point 1 that is only true if one is using a speed sensor and the other is using GPS. RideWithGPS and Garmin will use the same sensors. I don't think a speed sensor is more accurate but it's faster responding to speed changes.
Yes, this is my understanding. I think over long distances, GPS is probably more accurate, depending on how well the speed sensor is calibrated.
I like the "instant" speed feedback. I do not really need it. Sometimes I like to try to hold a speed on a climb and the instant feedback is useful. In another thread, someone mentioned that they like the instant feedback for when it is their turn to pull on a group ride, they can hold a more steady speed.
It is also my understanding that some higher end cycle computers use both a speed sensor and GPS to deliver the best of both worlds.