Keith is a Java developer.  Mark is a JavaScript developer. (I know them both personally so I feel pretty confident making this statement) :)

That does not make one "better" over the other.

If this is a strictly performance question then as a rule you are going to get the best performance with a mostly Java solution (where Java does the heavy lifting of sourcing the data).

That being said, if Java is a barrier to entry, the use the javascript approach while coming up to speed on Java.

Bottom line is if the JavaScript solution was not "performant enough" then folks would not be using it and ALOT are.

Paul, Thanks. What do you think about Domino Data Services to create the data? I would assume that using a native Domino API would be much faster than Java?

I understand that "better" is subject to opinions, and I was kind of looking for those too.

Java was the barrier to entry. I tried using keith's code and ended up crashing the HTTP task on my server. My own fault, but you have to break a few omelettes before you can make any eggs </jk>

Unless you need the json/xml then there are more efficient ways of getting to the data natively in XPages.  I view the rest services more for "external" consumption than for working with the data "locally' in my application.  

I would encourage you to keep "breaking those eggs" as the rewards are typically very high !!