The difference is that you can adjust your involvement to your liking. The role of an LLM in your writing process is what you want it to be. It could be as large or small as you consider appropriate.
Think of it like writing by hand vs. using a computer with good writing software. You can’t really reorganise your manuscript if it’s written on paper, now can you? That would require rewriting the whole thing. Also, spell checking takes a lot of time, and you probably won’t even notice your grammar quirks. Computers make writing easier and faster. An LLM is another tool, just like the simple editing features we’ve taken for granted for the past 30 years. Ask again in 20 years and people won’t even think of writing without an LLM, just like writing a report by hand is completely absurd today.