Barry,

Suppose that a few radio stations and internet sites like one or two of the songs you wrote. And they play those songs lots. Performing Rights organizations (SOCAN in Canada) monitor broadcasts and collect money from the stations that play your material. They give that money to you. All three you mentioned are good. You can Google each organization, do some reading, ask a few questions and then decide.

Suppose--just for the hell of it--that some TV show decides a song you wrote needs to be played at least once in every show they do (OK, I did say 'suppose', but sometimes dreams DO come true). That is mucho bucks. If you belong to a PR organization, they will collect the cash on your behalf. By not joining you could lose one shitload of money.

Say the gains are more modest. Let's say you'll make a few hundred in the first year and only $80/year in the next five. You got some reason you don't want six or seven hundred dollars?