GrowthBook vs Statsig

Verdict

Both read experiment results directly from a customer's data warehouse — a deliberate departure from flag-first tools like LaunchDarkly that only see their own SDK telemetry — and both offer a genuine choice of statistical engine with CUPED variance reduction. GrowthBook is MIT-licensed open source, warehouse-native by default whether self-hosted or on its managed cloud, offering a Bayesian engine (uninformative prior by default) and a frequentist engine with optional sequential testing, plus automatic checks for sample ratio mismatch.

Statsig is proprietary and can run on its own event pipeline or, on Enterprise plans, in a warehouse-native mode — so warehouse-native is an upgrade path rather than the default architecture. It offers three analysis modes (mixture-SPRT sequential as default, a dedicated SPRT mode permitting unlimited peeking, and Bayesian), with automatic CUPED applied by default using a stratification approach.

Choose GrowthBook if

• You want warehouse-native experimentation without a separate event pipeline, on the free tier or self-hosted, from day one.
• Open source and self-hostability matter — you want to inspect the code or avoid vendor lock-in.
• Your team wants a straightforward choice between two well-understood statistical engines (Bayesian or frequentist-sequential).

Choose Statsig if

• You want feature flags and a full event pipeline in one product, with warehouse-native as an option rather than a requirement.
• You want a dedicated SPRT mode that permits unlimited peeking without needing to plan a fixed sample size in advance.
• Session replay is useful to you — Statsig bundles it into its Developer and Pro tiers alongside experimentation.

What they share

Both apply CUPED variance reduction automatically or by default, both offer a genuine choice between Bayesian and frequentist-sequential analysis, and both are explicitly positioned against flag-only platforms that lack warehouse-level metric governance. Both also list each other as direct alternatives.

The honest caveat

Statsig's warehouse-native mode is gated to Enterprise plans, so if warehouse querying is the reason you're evaluating this category, confirm the actual tier and cost before assuming it's included. GrowthBook's free self-hosted tier is genuinely free, but is limited to a single project — budget for Pro or Enterprise pricing once you need more, and either way, factor in the engineering time to host and maintain it yourself if you go the self-hosted route.