webapp2 vs. Sane Stack vs. Yii

webapp2 is a simple. it follows the simplicity of webapp, but improves it in some ways: it adds better URI routing and exception handling, a full featured response object and a more flexible dispatching mechanism.

A full web development stack written in Javascript, integrating Ember.js, Sails.js and Docker

Yii comes with: MVC, DAO/ActiveRecord, I18N/L10N, caching, authentication and role-based access control, scaffolding, testing, etc. It can reduce your development time significantly.