My advise actually depends on your budget or willingness to spend money. If money is no object, I would go with the radar, AIS that both sends and receives, and a good radar reflector. If money is tight, then my priority order would be: good radar reflector; radar; AIS receiving capability; followed by AIS send capability.
First, you need to be seen and second you need to see what is "out there". Radar lets you see more of what is out there than any AIS. However, knowing what large vessel traffic is out there, who they are, course and speed, etc. as is available with AIS is a very good thing (however, don't own it myself yet). AIS broadcasting is only as valuable as there are units out there receiving the info and more importantly paying attention to your signal. Commercial traffic may not be looking for you either on AIS or radar! If you can afford it, it is still a go thing.
Just my opinion,
Tom
