I bought Garmin Vectors a couple years ago (before the P1 option) and am happy with that decision. While I am unlikely to move those bike to bike, I really like having 'normal freedom' to choose any wheels I want to chose and not have to mess around with them to get power. Right now I only have two sets but I can imagine acquiring a 3rd soon.

Based on my experience if your power readings against similar speeds on Strava are consistently high, then it probably is an issue with the readings.

dave