Most BigCommerce app builders on this list are managed or assisted services, so the vendor's team does much of the design and app store submission.
Check each vendor's track record. MobiLoud, JMango360 and Unbound Commerce have each operated for more than a decade and name their customers. Sandbox Commerce, AppShopo and Mapplico have few or no reviews and no named customers, so ask them for live apps you can download.
Choose between an app built on your site and a separate native app. MobiLoud builds the app on your existing BigCommerce site with a native layer, and Mapplico wraps the site in a WebView. JMango360, Unbound Commerce and Sandbox Commerce build separate native apps connected to your store.
Price the whole build, not just the monthly fee. Sandbox Commerce adds a usage fee tied to app sessions. JMango360 charges extra for add-ons such as native checkout and deep linking.