Hello Georgios,

Welcome to Intersoft Community Forum!

Comparing ClientUI and Prism is not apple to apple, because Prism provides only artchitectural and design pattern libraries, while ClientUI provides a multitude of MVVM-ready user interface controls along with advanced frameworks and design pattern libraries.

Based on our experiences in Silverlight project development, we don't require Prism when building apps using ClientUI. That's because ClientUI already has application framework that supports external XAP (on demand download), as well as integration with navigation and windowing framework.

I hope my explanation gives you insights on Silverlight frameworks particularly on ClientUI and Prism. Let me know if you have any questions.

Thanks,
Jimmy