Re: Drumset or Drumkit?
If you have a chair set or a chair kit, what is the difference? A chair set is a collection of chairs that belong together for one reason or another. A chair kit is something you buy at a store in a box, which contains the parts needed to put together one chair.
I think of drums in the same way. Either you see it as a collection of instruments all played together, like a classical multi-percussionist might view it, or you see it collectively as one instrument (albeit with many "parts" which come together to form the "whole").
Or, more realistically, you call it what you've heard it being called, and what has stuck, kinda like some people say "soda" while other people say "pop."