Cisco HCS platform is to be seen as a centralized UC platforms, that can be scalable as an IP Centrex solution and as rich in functionalities as a Cisco CUCM. If you're looking for a solution and your main focus is IM & P functionalities rather than voice, Lync is a good …
It is well suited for: Clients with call managers that want to continue using Cisco and want to minimize the new CAPEX. Clients that want to outsource the platform management and support. Clients that have a variation on the number of extensions. Although, Cisco HCS, is a solution that has a higher opex than the ones supported in ISP IP Centrex.
Cisco HCS platform is to be seen as a centralized UC platforms, that can be scalable as an IP Centrex solution and as rich in functionalities as a Cisco CUCM. If you're looking for a solution and your main focus is IM & P functionalities rather than voice, Lync is a good solution. If your focus is voice and telephony, Cisco is a better solution