Event tracking model
Winner: MixpanelGoogle Analytics 4
GA4 uses an event-based model but retains legacy concepts (sessions, pageviews, users) that constrain schema flexibility. Auto-collection handles standard events, but custom event parameters are limited per event and quota-capped, and retroactive schema changes do not backfill historical data.
Mixpanel
Mixpanel is built around flexible event + property tracking from the ground up. Any event can carry any properties, schemas evolve retroactively through Lexicon, and there are no limits on custom properties per event. This gives product teams the freedom to change tracking as the product changes.