Well, both Ionic and Onsen are made particularly for Hybrid Mobile Apps. You just won't be able to use it even for tablet apps without customization (If I am wrong, please correct me) just because they target the limited viewport and incorporate phone UX patterns.
Also, they are made with PhoneGap in mind (the apps will be hosted in the WebView component), and addresses some common WebView problems, e.g GPU acceleration for better performance.
If you need just some UI framework for a simple Web App you'd better have a look at Twitter Boostrap or Zurb Foundation. For a complex case you may even consider Sencha instead of Angular.