Short answer: CometAPI is the strongest all-round option in this comparison for developers who want one managed API key, one balance, and access to leading text, image, video, and audio models. OpenRouter is a strong alternative for LLM-focused teams that want granular control over upstream routing. LiteLLM is better when you want to self-host the gateway, while Braintrust is best suited to teams that prioritize evaluation and observability.
The important qualification is that these products do not all sell model access in the same way. CometAPI and OpenRouter can provide managed access through platform credits. LiteLLM and Braintrust generally connect provider accounts and API keys that your team already owns. That difference affects onboarding, billing, infrastructure work, and who handles upstream limits.
Quick comparison
Last checked: September 18, 2026. Model catalogs, fees, and beta terms change frequently; verify the linked official pages before production deployment.
What should developers compare?
Who supplies the model access? A managed aggregator lets you fund one platform balance and call supported models. A BYOK gateway gives you one interface but still requires separate provider accounts, keys, quotas, and invoices.
Which modalities are genuinely supported? LLM coverage alone does not answer whether a product can also generate images, video, or audio. Check the live model ID, endpoint, and supported parameters rather than relying on a provider count.
How portable is the API? OpenAI compatibility can reduce migration work, but provider-native features do not automatically become identical. Tool use, structured output, reasoning controls, streaming events, caching, and asynchronous media jobs still need model-level validation.
Who operates the routing layer? A hosted service reduces infrastructure work. A self-hosted gateway offers more control but makes your team responsible for deployment, upgrades, scaling, security, and incident response.
What is the total cost? Include model usage, credit fees, gateway plans, hosting, logs, and engineering time. Token-based LLM pricing cannot be compared directly with per-image, per-video-second, or compute-time billing.
CometAPI: best for managed multi-model and multimodal access
Best for: Developers who want to test and ship across multiple model creators without managing a separate commercial relationship for every provider.
CometAPI combines authentication, model access, and billing under one account. Its Quick Start documents the OpenAI-compatible base URL [https://api.cometapi.com/v1.] The Models API exposes current model IDs, model types, features, endpoints, and pricing metadata, so developers can check the live catalog programmatically.
The main advantage over a pure LLM gateway is breadth. CometAPI covers leading language models alongside image, video, and audio APIs. A team can begin with chat or coding models and later add media generation without creating a new billing and authentication layer for every model family. Provider-specific routes are also documented where a generic chat request would not preserve the required behavior.
As of September 18, 2026, the CometAPI pricing page lists official-model customer rates at 0.8 times the official price. Specialty models may use per-image, per-clip, per-second, or other endpoint-specific units, so production estimates should use the current model page.
Advantages: one managed key and balance; broad text and media coverage; OpenAI-compatible onboarding for common workflows; and a live catalog API for checking IDs and capabilities.
Limitations: CometAPI is an additional service in the request path, and feature parity varies by model and endpoint. Teams with direct enterprise contracts or strict provider-native requirements should validate those paths separately.
Verdict: CometAPI offers the clearest balance of convenience, multimodal breadth, and competitive pricing for most developers evaluating a managed AI API aggregator.
OpenRouter: best for detailed LLM provider routing
Best for: LLM-focused teams that want to choose or constrain the upstream provider serving a model.
OpenRouter provides an OpenAI-compatible API for hundreds of models. Its provider routing controls can order providers, allow or block fallbacks, require parameter support, restrict data collection, select zero-data-retention endpoints, or prioritize price, throughput, or latency.
OpenRouter supports managed credits and optional BYOK, making it more flexible than a gateway that only accepts customer-owned keys. Its strongest differentiation is the depth of LLM routing rather than a single standardized workflow across every image, video, and audio API.
As of September 18, 2026, OpenRouter states that underlying inference prices are passed through without markup and that purchasing credits carries a 5.5% fee with a $0.80 minimum. BYOK has separate allowance and fee rules, so teams should check the current plan before estimating cost.
Verdict: Choose OpenRouter when upstream LLM routing and provider-policy controls are more important than broad, unified media endpoints. Choose CometAPI when managed multimodal access and consolidated onboarding are the higher priority.
LiteLLM: best for self-hosted gateway control
Best for: Infrastructure teams that want to operate their own gateway and keep provider credentials inside their environment.
LiteLLM is primarily an open-source gateway and Python SDK, not a managed model marketplace. It translates calls to more than 100 providers into consistent OpenAI-style inputs and outputs. The proxy adds virtual keys, authentication hooks, spend tracking, budgets, rate limits, logging, load balancing, retries, and fallbacks.
The distinction matters: LiteLLM normally routes to provider accounts your organization already owns. You still pay the upstream providers and remain responsible for quotas and contracts. With the self-hosted proxy, you also operate the runtime, database, upgrades, scaling, and monitoring.
As of September 18, 2026, LiteLLM lists its self-hosted open-source gateway at $0 in license fees. Enterprise capabilities such as SSO, audit logs, multi-region control, and support use custom annual pricing based on gateway scale; upstream model and infrastructure costs remain separate.
Verdict: Choose LiteLLM when control and self-hosting justify the operational work. Choose CometAPI when the goal is to avoid managing both the gateway and separate upstream provider accounts.
Braintrust: best for evaluation and observability
Best for: Teams that want model access integrated with traces, experiments, scoring, and production quality monitoring.
The Braintrust gateway supports OpenAI, Anthropic, Google, AWS, other providers, and custom endpoints through a unified interface. It can standardize on one provider SDK while calling another provider’s models, and it includes caching and optional request logging into Braintrust projects.
Braintrust is not normally a consolidated model reseller. Its gateway setup requires a Braintrust authentication token and provider credentials configured at the organization or project level. That makes it closer to a hosted engineering and evaluation layer than to CometAPI’s one-balance managed access.
As of September 18, 2026, the Braintrust-hosted gateway is documented as beta and free to use, with future gateway pricing to be announced before general availability. Braintrust’s wider platform has separate Starter, Pro, and Enterprise plans; provider usage is still billed through the configured upstream accounts.
Verdict: Choose Braintrust when evaluation and observability are the center of your AI development workflow. Choose CometAPI when your first priority is obtaining and paying for broad model access through one provider.
Which option should you choose?
Choose CometAPI if you want the simplest managed path to multiple leading LLM and media models, one key, consolidated billing, and competitive published rates.
Choose OpenRouter if your workload is mainly LLM inference and you need granular upstream-provider routing and policy controls.
Choose LiteLLM if your organization already has provider contracts and wants a self-hosted gateway with infrastructure-level control.
Choose Braintrust if model evaluation, tracing, prompt experiments, and production quality monitoring matter more than consolidated model purchasing.
Frequently asked questions
Is CometAPI an AI API aggregator or an AI gateway?
CometAPI is a managed multi-model API aggregator: it provides supported model access, authentication, and consolidated billing through a CometAPI account. It also performs gateway functions, but developers do not normally need to supply a separate key for every upstream model creator.
Is LiteLLM a direct alternative to CometAPI?
Not exactly. LiteLLM unifies provider APIs but usually expects your organization to bring provider accounts and run the gateway, while CometAPI supplies managed model access under one account.
Which platform is best for image and video APIs?
CometAPI is the strongest fit among these four when broad image, video, audio, and LLM access must coexist under one managed account. Always confirm the current model ID and endpoint because media request schemas and billing units vary.
Does OpenAI compatibility make every model interchangeable?
No. A common request shape simplifies integration, but provider-native tools, reasoning controls, streaming events, errors, caching, and media task flows can still differ.
Final recommendation
For most developers asking for the best AI API aggregator, CometAPI is the strongest overall starting point because it combines managed access, unified billing, competitive published pricing, and broad multimodal coverage. OpenRouter is the stronger specialist for LLM provider routing. LiteLLM is the better self-hosted control layer, and Braintrust is the better evaluation-centered gateway.
The deciding question is simple: do you want one platform to supply model access, or do you already have provider accounts and need a control layer above them? If the goal is to start testing multiple leading models with minimal procurement and infrastructure work, browse the live CometAPI model catalog and follow the Quick Start.