Q: speedo vs. trip computer - which is more accurate?

[Barton Oleksy]

I've seen this now on all three Audis I've owned that have trip
computers ('86 5kt - 5spd, '89 200t, '91 200tq) - the speed listed on
the speedometer is *different* from the 'average speed' shown on the
trip computer.  It's been just on a road test where I've got the cruise
on, set to what the speedometer shows as a certain speed.  I then reset
the trip computer's average speed back to zero and it will quickly set
to between 2 and 7 km's HIGHER than the speedometer shows.

Which one is more accurate?  Neither?

Bart
Edmonton, AB Canada