It seems to me that those scripts that are saved as *.applescript are always meant to be the raw, uncompiled text while those that are saved as *.scpt can be either the raw text or the compiled program.
What advantages/disadvantages are there to using each extension?
An ancillary question: is there an analogous extension to *.applescript for the new JavaScript for Automation (JXA) language? Perhaps *.jxa?