So provide some alternate data. It looks like in all benchmarks I can find that compare the two, the iPhone comes out in anything from a tie to a significant advantage, except for one. If you run the benchmarks in parallel with the exact number of cores the S8 has, it eeks out a win. So near as I can tell, its the Samsung that can only win in a highly contrived scenario.
And this was last year's iPhone.
This is a very fast phone for an Android, though. If that is your world and basis of comparison, this speed bump will probably be significant. If you're already used to an iPhone, this one will start to get you close to last year's model, so isn't really going to satisfy you.