Compare benchmarks of CodeIgniter vs Yii

Although this does not directly apply to speed, we built an open source CRM application (Zurmo.org) using Yii. Before we started building Zurmo, we looked at Yii, Cakephp, Zend, and Codeigniter. We felt Yii was a great framework because it was lightweight, fast, and clean. It had a full set of functionality and matched up well with the other frameworks. We are delighted with the decision.

In your first benchmark : there is codeigniter 1.7.0 and Yii 1.0.2
After that codeigniter has many changes and in your second benchmark :
there is codeigniter 2.0 and yii 1.1.6

So latest codeigniter 2.0 is better than yii according to this benchmarks.

As per the market stats, Codeigniter is one of the fastest growing framework. Yii is in the initial release of the frameworks.Codeigniter has its own set of libraries whereas the Yii framework inherits the style from the three well known frameworks - Codeigniter, Symphony and Zend.Both of them have a concept of Lazy loading i.e. resources are only loaded when required.So it will be difficult to say which one is faster but they can be used as per the requirement of the product to be developed.