GrowthBook vs Statsig

GrowthBook

Everything my team needs is evidenced: a no-code visual editor, server-side and feature-flag experiments sharing the same model, namespaces for mutually exclusive tests, holdouts, multivariate, sequential and bandit tests, and edge delivery of visual and URL-redirect experiments that cuts flicker before HTML ships. Targeting runs well beyond the URL — device type, browser, UTM parameters and custom attributes are captured automatically. We found no public information on a personalisation capability or on personalisation that can itself be tested against a control.

Statsig

The no-code editor means my team can build client-side tests without a developer, and open-source SDKs in thirty-plus languages plus warehouse-native deployment give us server-side testing on the same flag and metric model, with layers, holdouts and autotune for experiment interactions. The captured pages are silent on edge or CDN delivery, on multivariate and multi-page tests, and on any documented experiment lifecycle or searchable library of past results.

GrowthBook

Both statistics engines are documented by name — Bayesian by default with a stated prior, frequentist two-sample t-tests — alongside CUPED in both engines, sample ratio mismatch detection, guardrail metrics, minimum-data settings against early calls, and a choice of Holm-Bonferroni or Benjamini-Hochberg corrections on the frequentist engine, plus a power calculator on Pro. Because metrics are computed in our own warehouse with every query visible in SQL, these are numbers I can defend to the board. Corrections apply only to the frequentist engine and sequential testing is named without documented peeking protection, which is what keeps it off the very top.

Statsig

Sequential testing, CUPED, Bonferroni and Benjamini-Hochberg corrections, winsorization and power analysis are all named in public — enough that I can tell the board which method decided each winner — and warehouse-native deployment lets finance re-run the analysis on our own data. We found no public information on sample ratio mismatch detection, on guardrail metrics that could stop a harmful test, or on a methodology write-up detailed enough to reproduce a result.

GrowthBook

The edge documentation shows a real consent-pending pattern: the visitor cookie is not persisted until a growthbookpersist event fires after consent, assignment runs on stateless hashing with no cookie needed, and sticky bucketing can be enabled per visitor only once the consent cookie is present. For my §25 TDDDG review the rest is silent — we found no public information on consent management platform integrations, cookie lifetimes, IP anonymisation, or guidance on the legal basis for testing in the EU, and the website terms state the service is for use only by persons located in the United States.

Statsig

The privacy notice lists cookie categories — essential, performance, functionality, advertising — and says Global Privacy Control is honoured where required by law, but we found no public information on what the test script stores or does before consent is given, no published list of cookies with their lifetimes, and no consent-platform integration or cookieless mode for a German deployment under §25 TDDDG.

GrowthBook

The trade-offs are documented honestly: the edge app's default makes a blocking call on each request that delays page delivery, with a push model to Cloudflare KV or a just-in-time cache to eliminate it, visual and redirect experiments running at the edge without flicker, SDK endpoints served from a global CDN, and a self-hosted proxy or own-CDN option. We found no published figures for script weight or impact on Core Web Vitals — '50% smaller SDKs' is a comparison rather than a number — so I cannot yet quantify the cost to our pages.

Statsig

A sub-millisecond post-init evaluation latency is published and the open-source server-side SDKs give an alternative path for flicker-sensitive tests, which lifts this above the basics. We found no public information on script weight, loading behaviour, anti-flicker handling or Core Web Vitals impact — and the one published figure covers evaluation after initialisation, not what the visitor's page pays.

GrowthBook

This is the standout: metrics are defined in SQL and computed in our own warehouse (Snowflake, BigQuery, Databricks, Redshift) with no PII leaving it, results are reproducible, and there is a full REST API across experiments, fact metrics, segments and per-experiment results, plus CSV download, an MCP server, webhooks, and tracking that integrates with Segment.io, GA4 and Google Tag Manager. We found no public information on stated API rate limits, and adjusted p-values are available only in the UI or CSV downloads rather than through the API.

Statsig

Warehouse-native deployment runs the experiment analysis in our own warehouse, and warehouse ingestion, outgoing integrations and a data export API are all listed — this is what lets me defend an uplift number with our own data when finance asks. We found no public information naming which analytics or CDP tools are supported, or on API rate limits and versioning.

GrowthBook

The contracting entity is GrowthBook, Inc. of Anaheim, California, the privacy notice has visitors consent to their information being transferred to and processed in the United States, US AI providers (Anthropic, Google, OpenAI, xAI) are named as sub-processors without stated server regions, and the website terms restrict use to persons located in the United States. The self-hosted, air-gapped deployment where no data or PII leaves our system is the one real mitigation, but we found no public information on EU hosting, an EU contracting entity, a published subprocessor list, or a DPA covering the cloud path — for a German team running tests on every visitor, that is nearly disqualifying.

Statsig

The contracting entities are Statsig, LLC in Bellevue and Amplitude, Inc. in San Francisco, the privacy notice says personal data may be transferred to the United States, and the only named processors are Google for login and Stripe for payments via Amplitude's site-wide notice; standard contractual clauses and the Data Privacy Framework are cited as safeguards. EU hosting is mentioned only within the enterprise warehouse-native offering, and we found no public information on EU processing of visitor data as standard.

GrowthBook

Public tiers are priced per seat rather than per visitor — Starter free, Pro at $40 / seat / month with unlimited experiments, feature flags and traffic — and the traffic-like limits that do exist are published with overage rates: managed-warehouse events at 1M or 2M per month then $30/M, CDN bandwidth then $1/GB, CDN requests then $10/M. Most of an annual invoice is therefore computable, but Enterprise is 'custom' and we found no public information on VAT treatment or minimum term.

Statsig

The traffic metric is events and it is unusually well defined: free at 2M events per month with no credit card, Pro at $150/mo with 5M events included then $0.05 per 1K events, overages billed in the next period, one-month auto-renewing terms, and taxes stated as the customer's responsibility — I can compute a Pro invoice myself, right down to how exposure deduplication works. Warehouse-native and standalone analytics sit on the enterprise Custom tier, so the full stack my team would actually want remains a sales conversation.