I found that my Vortex would read 20-70 watts high compared to two other power meters (stages and powertap). I started this topic:
Vortex owners might want to look at the youtube video linked in that topic. It has a lot technical info about the vortex power curve and which gears you have to be in to reach certain power levels. I never knew that about the vortex until I did the research.
The other thing I noticed about my Vortex is that as it warmed up, its power would drift higher and higher away from the other power meters. One’s best shot with the Vortex might be calibrating after you’ve warmed it up for 10-15 minutes. Of course, this is inconvenient during a workout.