I believe by 'we are using Adobe Mobile Service to track mobile app' you mean you are using Adobe version 4 SDKs and want to understand the benefits of moving to Adobe Experience Platform SDK (SDK v5).
If my understanding is correct, you can continue using the 4.x SDK along with the Mobile Services. However, it's support will end on August 31, 2020. So, it's recommended that you switch to AEP SDK (5.x SDK) as that will have to be done eventually.
Furthermore, the following document provides information about the differences between the new Experience Platform SDKs and the 4x SDKs. This will further help understand the benefits: