Using an Angular app as SAP Fiori application

As you mentioned, you are moving to SAP so it means you are moving to SAP HANA Cloud platform or backend SAP system. You can continue with just HTML Angular application that can connect to the backend via an OData service. 

Angular JS is JavaScript library that adds lot of features to your application. One thing to note here that if you are planning to use Fiori Launchpad, it could be an issue.

Following are the advantages/disadvantages of using angular framework:

Advantages

• Using Angular, you can develop complex High interactive rich internet web application.

• Angular application can be easily integrated with third-party library like Kendo UI

• You can easily manage the state of the UI objects and control over it

• You can easily perform Unit Testing

Disadvantage

• As far I know it is not possible to integrate an Angular application in SAP Fiori Launchpad

  You can also refer to this link for more details about SAP UI5 vs Angular framework −

https://archive.sap.com/discussions/thread/3744243