Ex Pres 

Average is definitely affecting not only by terrain, but by vehicular traffic, stoplights, etc. So you may normally ride along a flat road at 22mph, but your average for the ride might be 18. So which is more "accurate"? I would say the 22, but not because I'm trying to fool myself. But once you add in some bumps in the road (where I might ride at 8-10mph around here), then it's impossible to subtract out the "non-riding" variables.

I like to use averages when I'm doing the "same" ride over again, like our Tuesday night route. Even that's not perfect, but at least it gives me some baseline comparisons.