One is an established striker who has been on top for the past 5 seasons, while the other is a young gifted striker with a lot of potential who may or may not live up to expectations if he moves to a different league, thus I'd take Harry Kane over Halaand any day.
But it looks like age is already catching up with him. Can you tell us how his performance has been so far this season, except for enjoying playing against the likes of San Marino? 
I would go with Haaland. He doesn't need to be established. He has already announced himself as the lethal goal poacher of the next generation, and the biggest advantage is that age is on his side.