I've tried both, in the Cupra and in my Fiat Panda twinair, and can't notice any difference except in the wallet. 95 RON goes for 1,304€/l here, 98 for 1,476€/l.
At >40k km per year, and averaging 10l/100km, makes close to 800€ less fuel cost for the Cupra. For the Panda, at 8,5l and 20k km...