besides what Philip said (which is correct)

A PLB and a Ham Radio are basically designed for 2 different things. PLB is a "I NEED Help HERE" - not too much more information, but it gets through, and it's paid to be monitored

Ham Radio is a communications tool - does all sorts of communications besides "Mayday" - from "Hey, how are the fish biting" to "We MAY have a problem - you have any ideas on how we can get help before it's a Mayday?" The thing is, it's not full time monitored, and requires larger gear and antennas. There ARE things like the Maratime net which are active at certain times every day, but it's NOT pros, it's people who do it for the love of doing it

So there IS an overlap, but the overlap is rather small. It comes down to - what are you looking to do?