Ceramics are faster.  
 
Our Enduro ceramic bearings are ABEC5 quality and made in the USA.  These are simple to self-install in your drivetrain (you take a 3mm allen key and unbolt the old jockey wheel, you install the new jockey wheel, and you do the bolt back up) - simple and you dont even need to remove the chain.  
   
The ceramic jockey wheels are sold as a pair. 
    
Prices are in Australian Dollars.