asterisk users - Jun 2006 - A dual Asterisk server question

Greetings,

I am testing to connect two Asterisk servers. The IAX2 connection is
great to go. I used two different ways to make the call from one
server
to another, I listed both as following:
1. switch => IAX2/username:password@myserver/mycontext
2. exten => _xxxx, 1, dial(IAX2/username:password@myserver/${EXTEN},
60, r)

Could please anyone advise me which way is better, for performance,
call detail record, etc?

Thanks,

Tielin