I have personally used SBC 's and we do have MS lync integration.It is working well with both Avaya and Cisco PBX's.If deployed in HA pair, failover is quite easy and preserves RTP.
Advantages
1) Robust and resillent failover and stateful RTP failover .
2) More functionality .
Disadvantage
1) More steep learning , it will take you time and resources to master however CUBE config is very similar to IOS GW config.
2) Complex configuration .
3) Expensive.
Read this for more details
http://www.gossamer-threads.com/lists/cisco/voip/155673