Appian with Angular JS

As mentioned by SparshS, it's not recommended. SAIL is good and you get all the functionality of Appian functions which AngularJS obviously does not have.
You can still use AngularJS to create some forms and embed Appian using the Embedded interfaces. However, Embedded Interfaces should be used only if your main web application already exists, and you need a small subset of Appians functionality, say you want to embed some task report etc.
If you use AngularJS, you will have the responsibility of making your webpages mobile responsive - you can ofcourse achieve that using responsive frameworks like Bootstrap.
But then it will increase the efforts required - you will need custom code development.

On the other hand, if you develop the UI using SAIL, Appian takes care of mobile responsiveness, no extra coding(advanced CSS, JS knowledge) is required.
You also have the full flexibility and power of Appian expression functions. You will not have these advantages if you use AngularJS.

As mentioned by SparshS, it's not recommended. SAIL is good and you get all the functionality of Appian functions which AngularJS obviously does not have.
You can still use AngularJS to create some forms and embed Appian using the Embedded interfaces. However, Embedded Interfaces should be used only if your main web application already exists, and you need a small subset of Appians functionality, say you want to embed some task report etc.
If you use AngularJS, you will have the responsibility of making your webpages mobile responsive - you can ofcourse achieve that using responsive frameworks like Bootstrap.
But then it will increase the efforts required - you will need custom code development.

On the other hand, if you develop the UI using SAIL, Appian takes care of mobile responsiveness, no extra coding(advanced CSS, JS knowledge) is required.
You also have the full flexibility and power of Appian expression functions. You will not have these advantages if you use AngularJS.