When does it make sense to have your solution be a web app vs a mobile app or have both?
I've tried both and it's exponentially harder to do an App vs a website. Development is slightly harder, the main downside of an app are the hurdles surrounding distribution. With a website, you click deploy and boom - the latest version is available. Need to roll back a breaking change, easy peasy. With apps, it's so much more involved and everything surrounding it just cost more of your time.
If you're doing something by yourself, avoid doing an app if possible.
That being said, apps definitely provide benefits. Being able to send push notification reliably, and being installed on someone's phone does make your service more easily accessible to the users. Also, some services don't lend themselves to being websites. For example, if you need device capabilities such as GPS, Bluetooth or storage.
As usual, it depends on the type of application you're building. The app stores are a massive distribution channel and if you manage to be lucky in the ASO lottery and your app ranks high in the search results, the amount of organic traffic that you get is difficult to match.
You could do the same with SEO and drive organic traffic for your web, but an app should give you more exposition, according to research available via some googling:
research shows that 90% of their mobile time is spent in apps, and only 10% browsing the rest of the internet. In the ecommerce space, the contrast is even more glaring: mobile app users spend an average 201.8 minutes per month shopping, compared to 10.9 minutes/month for website users.
Depends on your customers, solution, market strategy, etc! Often apps give you more opportunities to touch your customers and involve them
In my opinion, a mobile app only makes sense if you want to access native functions of the device that you can't use via web app. However, the boundaries are now blurring as mobile browsers offer more and more features and there are also hybrid approaches like hotwire that allow you to access native features of the phone from a web app.
And currently still basically: game development only native.
I would always prefer a web app as far as possible, since you have many advantages with it: