OpenTok vs Twilio API for WhatsApp: What are the differences?

Developers describe OpenTok as "Enhance your products with live, face-to-face communication". OpenTok adds the clarity and emotion of face-to-face communication to your brand whether you're developing for the web, iOS, or Android. We make the integration of high-quality live video a breeze so that you can focus on building a great product. On the other hand, Twilio API for WhatsApp is detailed as "Reach users on the world’s most popular messaging app through one streamlined API, officially supported by WhatsApp". The Twilio API for WhatsApp provides developers all over the world with a simple, reliable, and officially supported way to use the WhatsApp Business API. They can now easily build messaging experiences that combine the ease of use of the Programmable SMS API with the global reach of WhatsApp.

OpenTok and Twilio API for WhatsApp can be primarily classified as "Communications SDK" tools.