Will you need to present your customers with relevant information based on where they are located right now?
For example, the mobile app Uber connects drivers with people who need to go somewhere.
Does your idea need to give people access to do something the moment it happens? For example an app that helps people track behavior or something they need to do away from the computer. If your idea connects people with information they need now, it’s likely building a mobile app will be the best route.
Are you looking to have a one up on the competition? If you’re building your product in an industry with similar competitors that have already taken advantage of building for the web but perhaps not as much for mobile devices, then building a mobile app could be a route to consider.