That's the point though Khan has always been ahead of Brook career wise and has never needed to fight him, I don't think the Porter win made Brook look anything special in the US because alot of people thought Porter won that fight, Golovkin smashed him silly and he arguably bottled it against Spence.
I think the majority of fight fans would watch Khan over Brook just for his attacking style and obviously the chin factor where he's always a decent punch away from being knocked out.
Brook for me has left it too late and has largely wasted his prime years worrying about Khan then going backwards fighting No Jo and Gavin etc, add to that his serious facial injuries (ones that have still yet to be properly punched on) and it's clear why he's still chasing Khan $$$
Just compare their fight records and they are chalk and cheese.