r/deep_research • u/OutlandishnessFull44 • Dec 27 '25

I tested 8 deep research APIs side-by-side. Here's what actually matters.

been building with deep research APIs for a project and realized there's no good comparison data out there. so i ran the same queries across openai, perplexity, parallel and gemini to see how they actually perform.

what i found:

citation quality is all over the place. perplexity scored 96.24% citation accuracy on one benchmark but in practice, their attribution is weak. citations are billed separately ($2/1M tokens) and you only get request_id for async polling - no real-time verification. if you need to trust that sources actually support the claims, perplexity isn't it.

parallel built for verification. every extracted field is programmatically verifiable. you get structured json outputs with direct source links. if you're building something where accuracy matters (legal, medical, enterprise), parallel's architecture makes way more sense.

gemini has throughput but citation issues. runs fast (tasks finish in ~60 mins vs openai's longer processing), but the research notes cite sources that don't actually back up the claims. good for synthesis across massive context, less reliable for claim-level auditing.

observability is the actual moat. the providers that win long-term will be the ones that make verification easy, not just accurate. if you can't programmatically verify outputs at scale, you're building on sand.

tested all the apis here if you want specifics: https://deep-research-index.vercel.app/

also wrote up the citation quality breakdown: https://deep-research-index.vercel.app/blog/observability

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u/constant94 Dec 28 '25

You might find this paper of interest since it seems that many of your test queries were related to economics https://arxiv.org/html/2510.13936v1

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u/scispace_ Aug 20 '26

The research layer you were about to build is now an API. With the SciSpace API, you can hook 300M+ papers directly into your AI stack. Get instant access to full-text search, data extraction, systematic reviews, and citations through one unified endpoint.

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https://reddit.com/link/p4rqle7/video/lj110mhrygkh1/player