AssemblyAI vs Soniox

The available facts cover API-level attributes such as batch pricing, streaming latency, WERWER - Word error rate - the share of words a transcription gets wrong; lower is more accurate., diarization, and compliance, but none address the attributes that decide the dictation use case: platform support for voice typing apps, local versus cloud audio processing, AI formatting and editing features, one-time versus subscription app pricing, or app integrations. Without any facts on these heavily weighted attributes for either AssemblyAI or Soniox, there is no basis to favor one tool over the other for this use case.

Both tools offer a HIPAA BAAHIPAA BAA - A signed Business Associate Agreement that lets you handle protected health information under US healthcare privacy law. and SOC 2 Type II certification, making them equal on the two highest-weighted compliance requirements. The differentiator falls on PII redaction: AssemblyAI offers it as a paid add-on at about $0.08 per hour, while Soniox does not offer PII redaction at all. For clinical transcription under US healthcare privacy law, the ability to automatically redact protected health information from transcripts is a meaningful capability advantage. Both tools support custom vocabulary for medical terminology. On self-hosting, AssemblyAI supports on-premises deployment while Soniox does not, giving AssemblyAI an additional edge on the second-lowest-weighted attribute. These two advantages together push AssemblyAI ahead in a use case where data handling controls are critical.

For recorded meetings and interviews, speaker diarizationdiarization - Splitting a transcript by speaker, so you can see who said what. and summarization carry the most weight. AssemblyAI includes both: diarization is available as a paid add-on at about $0.02/hr, and a summarization endpoint is fully supported. Soniox includes diarization at no extra charge but offers no summarization capability at all, which is a decisive gap at a weight of 4/5. On language coverage, AssemblyAI supports 99 languages versus 60 for Soniox. For long-file handling, AssemblyAI accepts files up to 5 GB and 10 hours, while Soniox caps files at 300 minutes. Word-level timestamps are equal. Soniox wins on per-minute pricing, but cost is not among the weighted attributes here. AssemblyAI leads on the top two attributes and also on file size handling and language breadth.

For a self-hostedself-host - Run the software on your own servers instead of the vendor’s cloud. deployment, the single most critical factor is whether a vendor actually offers a self-host or on-prem option. AssemblyAI explicitly supports self-hosting, while Soniox offers no self-host or on-prem option at all. This alone is decisive given the 5/5 weight on that attribute. Neither tool publishes facts on open weights licensing, hardware requirements, maintenance status, or model parameter counts, so those attributes cannot differentiate the two. Because Soniox cannot be self-hosted at all, it cannot serve this use case in any meaningful way.

For voice agents, streaming latency is the top-weighted factor. AssemblyAI claims 150 ms latency versus Soniox at 249 ms, a meaningful gap when the goal is natural turn-taking in a live conversation. Both tools provide a WebSocket streaming API, so that is a wash. On streaming price, AssemblyAI charges $0.0075 per audio minute versus Soniox at $0.002, making Soniox cheaper on that dimension. However, concurrencyconcurrency - How many phone calls the platform can handle at the same time. swings back to AssemblyAI: it supports 100 new streams per minute on the base plan compared to Soniox's 10 concurrent WebSocket sessions, which matters when scaling a voice bot fleet. Both offer custom vocabulary boosting. The latency and concurrency advantages together outweigh Soniox's pricing edge.