If you want to upgrade your existing Dynamics NAV solution, now you can use NAV Feature Comparison Tool with added NAV 2016 features.

You just need to select you current NAV release and system will compare it with NAV 2016 and you can see key differences. All of these can help you to decide upgrade or not for sure. You can compare all version from the release 4.

You can find this new tool on the following link:

https://www.microsoft.com/dynamics/upgrade-compare/nav/default.html