Your opinion needed! 1 in all app or multiple apps?

[IIIVIP]

I am developing 8 websites where users can discuss different topics related to different markets.

Website 1 - Trucks
Website 2 - Boats
Website 3 - Aircraft
Website 4 - Recycling
Website 5 - Concrete
Website 6 - Machinery
Website 7 - Oilfield

All content on the website will be available for Android & IOS apps. My question is,

Should we make 7 separate apps, each pertaining to a website?

Or

Should we make 1 app for all websites where the user can select what website they want to access?

By using 1 app

Pro's
Higher search rating
More reviews
Higher exposure to other apps

Con's
Difficulty finding the app since there are 7 website names
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