Best way I found is to test them both out to see how your 172 takes it.
Mine actually ran best on Sainsburys Super Unleaded. It ran very lumpy on Tesco, Shell & Motul Super Unleaded (Tesco's was ridiculously bad, thought something had broke on the car).
It ran fine with normal Sainsburys Unleaded, but I was getting better mpg from the super so I used that instead.