Multi-point pairing1. PX72. M33. IO6PX7 can connect to two devices at once and this works. You can quickly adjust these two devices in the app. This is not a big deal until you have to disconnect/connect between devices having had this luxury. IO6 seemed painful after using PX7. The M3 was supposed to do this too but it didn’t always work. It also annoyingly called each device a phone (“phone 2 connected”) regardless of what it was.Appearance1. PX72. IO6/M3PX7 and M3 are more obviously designed with external appearance in mind. Carbon fibre on PX7 is more discreet than it looks. IO6 is about as safe looking as possible. The exposed wires on the M3 seem out of place in 2019 regardless of previous designs. The cloth around the PX7 ear cups looks like it will attract lint.Battery life1. PX7/IO62. M3Estimates for PX7 and IO6 seem accurate. Ultimate the threshold for me is the duration of a long haul flight, which both meet with ease. M3 battery life is much lower on paper and lower still in practice. No more than 8 to 10 hours for me, which meant that I had to charge it on some flights.Portability1. PX72. IO63. M3M3 has to be folded up to be turned off. This is a terrible idea. You can’t keep it on a stand, hang it on a headphones hook or lamp during a flight. You can’t wear it around your neck. You can’t hold it in your hand by the band. The PX7 and IO6 has an ideal solution to saving power for people who forget to turn their headphones off: they go into standby mode. On the PX7 you can adjust this period.Case1. PX7/IO62. M3M3 has a thin, cheap-feeling fabric case that is no less bulky than the others. The cases are good for PX7 and IO6. PX7 case is more compact but IO6 case has a handle. Only IO6 comes with a flight adapter.