Oh, so I did read a bit, but of course you can support both Karpov's and Kasparov's match strength. I don't know any numbers (other than they played over 100 match games with each other) but I'd guess no one had more match experience than Kasparov... Fischer had very little... almost none at the top level.
Fischer wins. In keeping with his 187 IQ, Bobby was legend for his powers of detailed calculation, his precise feeling for position, his stamina, and his very quick play. Fischer was probably the best 'lightning-player" ever, and there was no better end-game player in the world.
Fischer did not have an IQ of 187. Just so you know.