The fact that you can tell them what exactly you want your app to contain, as well as incorporate your API to sync everything together, such as your website, email, reminders, gaming tournaments, etc.
Their pricing is slightly out of our budget and the delay in contact makes the project take time; most of the communication is done via email.
It's a great solution to application creation. The fact that we are able to synchronise our eSports tournaments and have a replica of our website in the app is quite powerful.