Ghosting is easier tonight and messier for a long time after.

Disappearing settles tonight by handing the whole thing to the other person. They have to fill the silence themselves, and people nearly always fill it with something worse than the truth. You end up carrying a small open loop around for months, and it has a way of turning up again in a corridor or a group chat.

Two sentences usually close it: what you have decided, and that you are sorry it took a while. You do not owe anybody a full explanation or a conversation you cannot manage. If you have already gone quiet on someone, saying it late still beats never.