.... This is somewhat off topic for a moment but like you I also run a GTI which was 200bhp K03 ex-factory but is Revo Stage 2 software plotting 270bhp consistently for years on the same rolling road. She has been modified (brakes, suspension, braces, carbonfibre body parts etc) and maintained by Volkswagen Racing for 'fast road use' and occasional trackdays. She is tuned for V-Power octane which is additionally a maintenance aid and I take the advice of professionals Volkswagen Racing and Revo (and JKM Performance, Milltek and others) when told to run her on V-Power for both reliability and longevity. An aftermarket APR high pressure fuel pump is also fitted. Such actions such as fuelling are all controlled by the ECU software and a modern digital camera has a direct equivalent.
Your car's engine doesn't differentiate between day-to-day use and trackdays regarding fuel - It does what you ask it to regardless of where it is being driven. Consistent fuel octane, not chopping and changing to and fro, is better for it in the longer term.
But to get back on topic, personally I strongly believe that it's always better to use and buy the best you can and that applies to cards, batteries, and anything else including lenses, filters, tripods etc etc etc. But, each to their own and we all have different attitudes.