For an eCommerce mobile application, you have two main options: using an app development agency or a mobile app builder. Agencies offer customization tailored to your specific needs, giving you a unique, scalable solution that can be costlier. On the other hand, ecommerce mobile app builders are budget-friendly and quick but might lack flexibility for complex requirements. If your site requires unique features or integrations, a custom solution might be best; otherwise, an app builder is ideal for standard functionalities.