Uhoh, definitions again. Always fun as folks look at things differently. Here's my take:
SP is Service Provider who could either be MA or escort, it is a general catch-all for sex workers. Let's face it, both categories provide services. For an MA to be in the SP category she (or he) would have to have a sexual component.
MA does massage and could or could not be an SP depending if she offers a happy ending of some sort. Some MA venture into Escort territory and call themselves hybrid.
Escort does FS and other things an MA does not, or is not supposed to do :biggrin-new:
However, most will use SP to describe an escort more often than MA.