You’ll find a lot of negative reviews of the Vector 3s based on their early roll out, which Garmin screwed up (akin to Wahoo’s screwup with the 2018 Kickrs and Kickr Cores). Since changing the battery covers (which you shouldn’t have to bother with purchasing today) and using their tip to apply baby oil to the batteries, I’ve had zero issues. The ability to use one power meter on two bikes has been very helpful. The reviews and feedback for the Favero Assiomas are also very good, so those might be worth looking into. As a Garmin user already, you’ll get some cool (albeit not terribly useful right now) metrics from the Vectors. I think both products are high quality. I don’t know a damn thing about the PowerTap P1s other than what I’ve read on DC Rainmaker.