Don't confuse GPS accuracy with tracklog smoothness.
For example, if you are standing at the point of 50 degrees 0 minutes north, 120 degrees 0 minutes west, and if your GPS receiver reports 50 0 0 N 120 0 0 W, then that is real accuracy.
Tracklog smoothness is rather different. All GPS receivers use Kalman filtering to smooth the result display, or to get it to throw out the spikes, so to speak. Different receivers use different factors in their Kalman filtering somewhat depending on the purpose of the receiver. For instance, the GPS receiver in a jet fighter is going to have different filtering from the receiver in a hiker's handheld unit. Besides, if you walk a specific route five times, and if all five tracklogs line up perfectly together, that doesn't mean accuracy. It might mean that all five tracklogs had the same error.
Too many times, the error, or lack of accuracy, is really the fault of the underlying map database or the datum of it.