COMPARISON
One measures what was done. The other measures what changed. The marketing industry has built an entire economy around confusing the two.
Activity-based measurement is the default because it serves the people doing the marketing, not the people paying for it. It is easier to report, easier to manipulate, and easier to defend. Outcome-based measurement serves the business, but it requires honesty, access, and the courage to say 'this didn't work' when the numbers show it.
The best marketing companies report on outcomes. The rest report on activity. And the businesses that cannot tell the difference pay for theater.