If we were ready to spend 100 million on Sancho, I'd throw 120 million at Kane without hesitation.
He's a better, more rounded player than Haaland. Haaland is very much a goalscorer, while Kane would help us create more chances while still scoring a similar amount of goals.
He's also England's talismanic figure and would be the perfect player, from both a football and a branding perspective, to lead this United team with a core of young, English players. As the senior star player he could very well be the cog that put us on par with City. He's that good.
If it's between Kane or a backup RB + a CB that may or may not become a starter + another Cavani esque depth striker, I'd go for Kane, no question.