Arena (formerly Chatbot Arena) vs Braintrust

Arena, formerly Chatbot Arena, is a free web platform for evaluating AI models by comparing responses and collecting votes for public leaderboards. In Battle mode, it presents two anonymous responses and reveals the model identities after a vote. Arena aggregates qualifying votes with the Bradley-Terry rating system. Side by Side and Direct modes are also available, but only anonymous Battle votes count toward official rankings. Leaderboards cover agent, text, web development, image, video, vision, document and search tasks; comparisons include image generation, image editing and video generation. Leaderboards can be viewed without signing in, while Direct, Side by Side, Image Arena and Video Arena require login. Accounts can use Google or email, and coding Agent Mode can connect to GitHub repositories. Arena applies a daily usage limit that resets 24 hours after it is reached. Video Arena requires login, permits two generations per 24 hours and offers Battle mode only. Arena also provides commercial evaluation services for enterprises, model labs and developers, with results supported by service-level agreements. Conversations may be used in research datasets and private provider evaluations; shared data is de-identified, and Arena advises against submitting sensitive information.

Braintrust is an observability platform for teams running AI agents in production. It lets teams inspect agent traces and tool calls while tracking latency, cost, and quality in real time. Users can evaluate datasets, compare prompts and models, and score outputs with LLMs, code, or human reviewers. Discovery tools surface patterns in production traces to help investigate agent behavior, and the Loop agent can run evaluations, generate test cases, and iterate on prompts autonomously. Braintrust lists native SDKs for Python, TypeScript, Go, Ruby, C#, and more, and its MCP server lets coding agents query logs, run evaluations, and update prompts from an IDE. Security options listed include SSO, RBAC, and hybrid deployment; Braintrust states that it is SOC 2 Type II certified and GDPR and HIPAA compliant. Starter is free, with 1 GB processed data, 10,000 scores, and 14-day retention. Pro costs $249.00 per month; Enterprise pricing is custom.