Which attribution model should I use?

Use data-driven attribution where it's available, and don't agonize over the choice — the model matters far less than the completeness of what you're measuring. No model can credit the phone call or closed deal it never saw.

Attribution models only redistribute credit among tracked touchpoints: last-click flatters bottom-of-funnel search, first-click flatters awareness channels, data-driven splits credit statistically. If calls, offline conversions, and cross-device journeys are missing, every model confidently misleads you.

The working rule: fix measurement coverage first, pick one lens, and use it consistently — a stable, slightly imperfect model beats switching models until the report says what you hoped.