Jasmine
Pros :
- Well documented and supported
- Built-in spies
- RSPec-ish DSL
- Nice integration with other tools
Cons :
- Pollutes global namespace
- Not built for NodeJS
Vows
Pros :
- Clean and meaningful syntax
- Created for NodeJS (ie. Asynchronous Testing)
- CoffeeScript (it is really beautiful with)
- Watcher out of the box
Cons :
- Documentation (eg. teardown functions)
- Batches & Contexts can be odd when beginning
- No built-in spies (SinonJS ftw)
I would prefer Vows for testing NodeJS applications and Jasmine for client side code. Once you get used to CoffeeScript, vows becomes really clean and powerful.