If the argument does not survive being written down, it will not survive the room. That is the entire reason I write a memo before any meeting where a decision is expected — not to inform people, but to find out whether I actually have a position.
Most of the time I do not. The first draft reveals that two of my three reasons are the same reason, and that the thing I was going to lead with depends on an assumption I have not checked. Better to discover that alone on a Tuesday than in front of eight people on a Thursday.
The meeting then becomes shorter and worse-tempered, in a good way. People arrive having already disagreed on paper, so the discussion starts where it would otherwise have ended.