The Polar box does have a lot lot more parameters compared to the P3 but is harder to install and required me to take my windscreen wipers etc off to install it, wipers never worked the same again which I found annoying. P3 just plugs into the OBD port so much easier and the digital display looks good in the air vent. I chose the P3 primarily for the 0-60 function, but I believe the newer Polar may have this function too? With the Polar I didn't understand most of the numbers anyway so I don't feel like I need it in the R.