Overview

Javascript templating systems:

• Pure: non intrusive templating system with nice demo application - it is in my opinion a good choice
• Helma include its own templating engine
• Mustache has even more implementations
• JQuery Templates is a proposal by Microsoft and includes an analysis of existing frameworks - you can read more here
• EJS is another templating language which includes caching support and is part of JavascriptMVC
• JQote2 focuses on performance and seems to have some lead on this and includes flot plotting library
• Underscore seems to be the only competitor to JQote2 and includes many interesting utilities
• John Ressig has written Javascript Micro Templates

I also found some articles:

• a benchmark of engines shows little difference
• stackoverflow has various articles on javascript templates

Conclusion

As usual in JS world, there is more choice than developers. Future ERP5 client side rendering should be designed to be independent of the templating language choice.