A Google Business Profile gets you found. Your own site is what gets you chosen.
The profile does real work – it puts you on the map, shows your hours and collects reviews, and you should keep it accurate. But it shows a guest almost nothing about the thing they're actually deciding on. It doesn't carry your full menu, your story, your private-hire options or a form that reaches you.
There's an ownership difference too. Your profile lives on Google's terms, in Google's layout, next to your competitors. A
business website is yours, on your domain, and it's the link you put on every listing, every social bio and every menu board.
In practice you want both, pointing at each other: the profile gets someone within reach of you, and the site closes it.