What are the determining factors in selecting the signaling protocol?

I am running CM4.1(3)sr4d. All of the gateways on my network are configured for MGCP. I've put the ATA on the network already using SCCP and it was as easy as adding a new phone. I can't seem to find any information indicating why one protocol would be better than the other.

Hello,

perhaps not an explicit document, but the experience of many (admittedly, not including myself yet), is telling that H.323 is the preferred protocol. You can try reposting the question in "IP telephony" forum where it will have more visibility.