I would just assume that a website is better for getting new users cus of the lower bar to entry, theres no install, a lot of peoples phones are full. Also you can go from QRcode or clicking 1 link directly to the app.
Whereas with an app, you have a link or QRcode that goes to the correct store, then install on the store, and then open.
I get that an app would be better for retention, as they could put the icon on their desktop (or whatever it's called) But I assume a site would be better for getting initial visitors cus of much lower barrier to entry.