I don't know any benefits of making the switch, but can point out a couple of SIP highlights:
1. SIP uses a distributed model where the phones have variable levels of intelligence, such as being able to generate dial tone locally. With Skinny phones, the bulk of the intelligence resides on the CCM.
2. SIP promises a truly integrated network for voice and data because as a protocol, SIP was built from the ground up for that purpose. The protocol plays well with existing protocols such a HTTP, WWW and MIME.
It'll be hard to say whether there will be a benefit to making a switch. Both server well in the niche they are used.
Regards.
