Originally Posted by andr0id

If you and your friend are about the same size and weight, riding similar types of bikes with similar tires and you ride the ride together, your power will be +/- 10% or so. If Strava is telling you twice as much energy/power compared to the metered ride, then go with the meter.

I can almost guess from here... Let me try.

Hard ride in the wind, 50 miles.
So about 3-3.5 hours at 500 Kj/hour which is about 1500 Kj or 150-160 so avg watts or so...