It's funny that this should matter at all. If I only had one device I'd feel good about the data, thinking hey, I'm measuring power, the manufacturer claims it's accurate to within 2%, so this is cool, I actually know what performance I'm hitting. And then for the same power output I'm getting different results that are much greater than the 2% accuracy claimed by the manufacturer. In other words, the power meter may be 98+% accurate to what my body is actually doing, but I'm not getting that level accuracy reflected in my data due to how it's recorded. Doesn't matter really, but it is the kind of thing that will bug me. I'd almost have been better off not knowing, but for some reason I recorded the rides on both devices just to see what the data would look like.

Uploading rides through the Fenix 5 is much more convenient, since it's paired with my phone and auto-uploads activities as soon as I stop and save them. They show up in Garmin Connect and then Strava within seconds. With the Edge 500 I have to unmount it and plug it into my computer over USB. I do like looking down at the Edge 500 during rides, though, as opposed to having to look down at my watch on my wrist. I may find myself using both, and only uploading the rides through the Fenix 5, but looking at the data on the Edge 500 during the ride, then discarding it after the ride is over. That means all my historical data that's uploaded will be from the Fenix 5 from now on, which is the one showing the lower power output. It's still fine, but the ego is slightly annoyed by this.

One thing I haven't yet tried is disabling auto-pause on both units. I turned on auto-pause on the Edge 500 a long time ago because I was sick of having my average cadence data being skewed by periods of time when I was stopped at intersections and the like. The data still gets skewed a little by the time spent not pedaling as I coast into intersections, but at least it's skewed less by eliminating the time I'm actually stopped.

What I really want is a setting that says, essentially, that I want both cadence and power averages to be calculated only during periods of time where I'm actually pedaling. I want to know what I'm doing when I'm actually doing it, and am annoyed that my averages don't reflect what I did when I was busy doing it due to times when I wasn't doing it at all being included in the average.