First thing, lets clear up what I mean by "garbage" edit:
A garbage edit is when completely random text/code has been inserted into a post. This leaves the post making no sense at all. The most common occurrence of these types of edits are the "tests" that we have to endure every now and then in the review queue (which lets be honest, stand out like a sore thumb anyway).
Although, from the test point of view the rejection reason doesn't matter (all that matters is that you reject), what reason should be taken when this kind of edit occurs genuinely?
The two options I am always torn between is "Invalid Edit" and "Radical Change" - and I have started to lean more towards "Radical Change" as, in my opinion, the edit changes the meaning of the post.