FTP tests are PoundSign Awesome as are 40K Time Trials...Hurt now and puke later
Consistency needs to be the order of the day.
My Stages meter ran ~8% higher than the Powertap pedals I am currently using. In addition, the PowerTap pedals also ran about 5% higher than a PowerTap wheel on an FTP test where I had them both going with two Garmins and none of those matched what the Computrainer read. 3 devices 3 numbers.
Stick with one power meter is what that test told me. All data is then relative to each other.