While AIS is a nice tool you are presuming that ALL vessels in your transit are is participating. This is probably not the case. AIS depends on the participation of others to provide information to you.
Radar is an active instrument giving you a real time image of objects around you. While there are situations wherein objects may be masked on radar it is fewer occasions than a vessel not having AIS. A properly tuned, quality radar system will display some pretty small objects. I routinely see fishing floats at greater than a mile out.
You don't really need a "pole" if you don't want it. There are mounts that fix to the backstay.
If it came to a choice of a chart plotter or radar I'd choose radar. Inshore you can navigate by radar a chart plotter won't tell you that you are about to be run down by that cigarette boat.