Multi-cast and uni-cast messages are the same except for the IP address. The IP addresses for multi-cast are predefined in the ACN E1.31 specification. Uni-cast is not in the specification for ACN E1.31. This was added for the original San Device controller that used a Wiznet Ethernet adapter. This adapter only supports 6 connections or six IP addresses. So using this controller limits you to 6 universes of data in multi-cast mode.
When you use uni-cast, the computer sends out an address resolution packet (ARP). The controller responses with the MAC address to create a link to the computer. With uni-cast your router will know which port the computer is on and only send the messages to the correct port. If a message is broadcast, it will go out all of the ports. If the controller supports the IGMP message sets, it will tell the router which ports it is support for broadcast messages. So in the end, there is very little difference between the two message sets. To maintain the simplicity of my controllers, they do not support the IGMP message sets.
It is recommended that you use a separate network or a Falcon Pi player for your show. This way your internet traffic does not interfere with the timing of your show messages. In reality if you don’t have a large show it really shouldn’t matter, it is just best practice.