Mobile apps have features that make them more convenient than websites: instant loading or push notifications are just a few of them. But HTML5 is bringing most of these features to mobile sites and making it possible to provide the same app-like experience in web apps.
Some people won't download an app because they don't like it or already have too many, but others will find it more handy than accessing an URL.
Each solution has its own benefits, and no option is better or worse than another as it will always depend on your users' needs. You can use both solutions and see which one works better for you, or choose the one you already know is right for your customers.