I have a PP5, but it kinda sucks. I've already updated the FW several times, but there are still weird bugs. For example if I let it sit for too long, it just stops recording ride data. Also it has weird speed spikes if I pedal abruptly. I'd definitely consider getting something else. The PP6 needs to have eliminated all those issues for me to even consider getting one.
Though I did get mine for really cheap including the crankset, and it's the only reason I'm still tolerating it.