Cartesia

When latency is your make-or-break metric, Cartesia is the obvious starting point. Its Sonic-3.6 and Ink-2 models top the Artificial Analysis leaderboards, and if you've heard voice agents that feel unnervingly human, there's a decent chance they're running on this stack. The fact that both TTS and STT shine at once is rare — most rivals excel on one side and lag on the other. Where it really wins is the full-stack story. Managed Agents isn't just a bolt-on; it's built on the same models, so you avoid the integration lag that hits other platforms. The per-minute call pricing at $0.06 plus telephony is transparent and competitive, especially when you compare to the per-character or per-hour fees some competitors sneak in. Then there's deployment. If you're in banking or healthcare and need data to stay inside a VPC or on-device, Cartesia's in-region inference is a lifeline. That's not a nice-to-have; it's often the only way you're allowed to use cloud AI at all. SOC 2 Type II and GDPR compliance back that up. But the credit system takes some math. You're juggling credits for TTS/STT and prepaid agent dollars, and the FAQ hints at rollover rules that could trip you up. It's more complex than a flat per-minute rate, and for hobbyists or casual users, that's friction. For real-time needs, Cartesia beats ElevenLabs and Deepgram on speed and accuracy, but those tools have simpler pricing and broader integrations for non-real-time content work. If you're dubbing a podcast or generating voiceovers in bulk, you don't need state space models — you need a friendly editor and a credit card that's easy to reconcile. One more thing to watch: overages. If you blow past your credits, you'll be charged, and the rate isn't always obvious until you hit it. Read the billing docs