Whether Strava's estimates of avg power are accurate or not (and they don't seem terribly accurate to me), just knowing the average power number for a ride isn't worth all that much. And as far as I can see this is all that Strava can give you unless you input data from a power meter. And HR can be way more useful when paired with power data. To find out if I am a better rider this year than last I don't think I could do that from HR alone.

I love using my power meter. Especially on the trainer....even though I don't race.