I'm not saying Brook is shit infact I do rate him highly and he has skills but he hasn't fought at Khans level yet.
Amirs been in situations he hasn't and has way more big fight experience and has faced way more varied types of opponents style wise.
Styles make fights so all this He beat him who struggled wth him etc bullshit means fuck all at the end of the day. Brook and Khan have taken completely different routes and not shared an opponent along the way to my knowledge so saying one would beat the other judged on who they have fought fighting someone the other has fought is crazy talk.
Ali lost fight 1 to Frazier
Frazier got absolutely obliterated by Foreman
Ali beats a prime Foreman

Proves that theory doesn't work