I think general concensus says PES, I am not really a football game player but both are good.
My brother and I call it ISS as PES is just about 7 or 8 sequals after the original International SuperStar Soccer for the SNES. He once had a arguement with someone about what awas better, the new ISS or the new PES...only later did they realise they were argueing for the same game.
Hmm, pie.