Best SDK for implementing whatsapp-like videochat?

What is the best way of implementing a whatsapp-like videochat and textchat into ones own app? Reliability, ease of integrating and documentation and lastly pricing.

• Agora: link
• Twilio link
• Sinch link
• Opentok/Tokbox link

I use https://connectycube.com

They have iOS(Swift), Android(Kotlin/Java) and web version(pure JS and Cordova for mobile browser). They use WebRTC to manage video calls, works fine for now.

Main features:

• 1-1 video chat
• Group video chat
• Cross-platform
• WebRTC based
• Screen sharing
• VP8/H264 video codecs supported
• Mute/Unmute audio/video stream
• Switch video input devices (cameras)
• Video recording

They have ready-to-go guides and code samples on GitHub for each platform:

• iOS video calling guide https://developers.connectycube.com/ios/videocalling
• Android video calling guide https://developers.connectycube.com/android/videocalling
• Javascript video calling guide https://developers.connectycube.com/js/videocalling