Well said above.. A couple of additional considerations....
- Performance / Cost ratio may be higher with the Unifi setup and future upgrades
- Unifi GUI likely offers more network transparency, ease of management and control for the end user
- and many users, including myself, use it with C4 systems with no issues. For someone already with a Unifi setup, it seems logical to stay put and just find a C4 dealer that is comfortable in working in that network environment which there are many.