IIRC PowerPod is based in Lovely Flat Florida. In flat terrain doing TT/Triathlon type training, I’m sure it’s plenty good for steady state and interval training.
I live in a place with rolling terrain + some steep climbs. I started out with PowerPod and shifted to Quarq after 12 months. For my use case there is no comparison: Quarq wins hands down. PowerPods were definitely overstating power on downhill spin outs. Also would get insane transient power spikes when dropping outer pedal to corner at high speed.
Thinking about this more, another issue is simply road surface quality. PP has settings for this in the software, but bumps and thumps probably don’t just affect rolling resistance part of the balance of forces calculation ... also going to have transient effects on the ability of the system to determine whether or not one is (say) going downhill or level or uphill — suspect this caused transient power spikes as crank rotation when spinning out would then look like big power input.
Anwyay, if you really want to be *sure* and you don’t just ride flat good quality roads, buy a crank-spider type power meter and live happily ever after.
PS: If I were interested in my aero performance, I’d buy one for the CdA measurement feature. Absolutely. They’re a good company and provide good forum support. Just not for me for my use case.