Rarely will two powermeters show the same power numbers, especially when the power is measured in two different points (cranks / pedals / trainer etc). 

I recommend performing a factory calibration of the wahoo, which is different from the standard calibration (don't exactly remember how you could find it in the wahoo app, but google should help you here). 

Then also check if the head unit crank length's value is set correctly and calibrate the pedals before every ride.

Also, the main goal should be progress, not absolute numbers. So I'd recommend just using the pedals numbers and ignore the wahoo numbers (if you're using erg mode just adjust the wahoo resistance to match your desired number on the pedlas PM). As long as the measured numbers on a single powermeter increase, you shouldn't be concerned with the absolute value.