I am about to replace just the rear tyres on my 2003 Boxster S. The OEM tyres were Yokohama 265/35 ZR18-N1. Since I am only replaccing the rear two, my intention was to get the Yokos again. The discount places in the UK don't seem to do these in Porsche N1 spec. The choices are therefore to pay about £60 ($100) per tyre more, get a different brand in N1 spec (then I will have different brands front and rear) or get the Yokos without the N1 spec.
What is the disadvantage of the last option?