I have Raymarine Axiom 12 that came with the boat when purchased in 2020.
No Autopilot, no AIS. For our Great Loop starting the next May 2021, I added AIS receive with Raymarine's VHF73. It was great especially in places like NYC and going up the Hudson, where many of the ATONs are AIS equipped. (I also added Autopilot).
On the rivers south of Chicago, it did not take me long to realize I wanted AIS Transmit as well. Having other vessels call me up on the radio BY NAME is extremely valuable. Seeing tows "around the corner" on windy rivers, before you can see them or before they appear on radar is incredible. Being able coordinate passing with large tows on the rivers is very valuable.
I selected the Em-Trak B924 ... the WiFi is nice so in the mornings, while having my coffee in the salon, I can see if there is any commercial traffic approaching the lock that I'm near. I don't have to go upstairs to the helm to see what's happening on AIS. I also did not want to add a THIRD VHF antenna to the boat, so the model I selected has a built in antenna sharing capability with one of the VHF radios.
There is a simple NMEA 2000 adapter cable that goes between the Raymarine network and the Em-Track B924.
FMI:
https://shellerina.com/2023/09/19/ais-ing-again/
There is even a phenomenon called VIRTUAL ATONs... They are rare. I've seen only one. Basically it puts an additional "buoy" on the chart plotter via AIS where there is NO actual buoy!!! It was very bizarre the one time I saw it. But I googled around, and learned that it IS an actual thing that the Coast Guard deploys in certain places.
I think the logic is this, many times a single ATON (red or green) is adequate, but two ATONs would be better. It does not "cost" anything to add a second VIRTUAL ATON to pair up with the first one in certain situations where it makes sense. The AIS transmitter on the one real buoy is simply sending out two beacons with the Lat/Long and other info for the second.