Rasa or Botpress to build the chat bot if you’re on a budget, is supported for voice and is open source. For LLMs, Hugging Face is great, for extraction from PDFs Baystack is great!

Google and Microsoft’s are all commercial options and they’re fine for testing, but they can get expensive as you scale. The flexibility on no costs, but definitely more work on setup side with open source. Basically it comes down to having features and budget.