I've previously posted about both NDI and SRT, they are great video transmission protocols. Both are unicast by default, but can support multiple clients or players. There are some differences that might make you choose one over the other, here are a few that I can think of:
SRT is open source, NDI is royalty-free
SRT is low latency, NDI is very low latency
SRT can work over WiFi or across public internet, NDI works best over gigabit LAN
SRT support is coming to OBS, NDI is available in OBS via a plugin
SRT seems to be supported by more digital signage players
NDI seems to be supported by more cameras
For myself, I'll continue to implement both for different use cases.
Please comment below about missing information or errors.