IAX2 vs Sip

I am looking at the differences between IAX2 and SIP. I am currently using voipms and it supports both. Which is better for freepbx? I have read IAX2 requires less bandwidth and uses only one port. Is there anything else you can tell me? Which one would you use? Unfortunately my location has ATT DSL so my internet upload is about 5mbps. Maybe IAX2 would be better?

Thank You

Maybe to get you started:-


For IAX read IAX2 which is an improved version.