[Asterisk-Users] Problem with chan_iax.c implimentation causes bad audio?

[Matt]

I received an e-mail from a vendor who says:

"We have recently become aware of an issue in the chan_iax2
implementation of IAX2. This issue leads to degraded audio quality.
Due to this we are urging everyone to move to SIP."

I don't want to discount what this person is talling me, but I'm
curious to know why I would only be having issues connecting to his
servers, and also what exactly the issue is (if anyone knows).   I was
always under the impression that IAX2 was a better way to connect
servers and was more advanced (jitterbuffer/etc) then sip was.

Can anyone comment on this?