The scripting plugin is something you have to add into MC (as an add-on). And the script would then have to be written in the language supported by the scripting plugin. And it will only work on MC for Windows (but that might not matter to you).
pscriptor is a command line tool that works on all the platforms, and the scriptlets that are written are pretty simple for the most part.
The difference is that pscriptor must be run manuallly by you, when you want something to happen. The scripting plugin can use various notifications that MC supports to take actions when something happens (I haven't spent much time with the MC plug-in interface), so the user experience is probably more integrated.
You should use whatever method works for you, and that you feel most conformable with. I wrote pscriptor to do things that weren't easily possible, in a cross-platform way, but that means it requires some command line usage.
I'm all about Getting Things Done, and most folks are that way, but some add the amendment "... But Only If It Looks Pretty".