Google Sign-in Button, Chatfuel, Their Usefulness and Trade-off

Google Sign-in button:

• Usefulness: 
• Visitors don't need to create accounts, visitors are very lazy nowadays. This catch more visitors than enforcing the to register to use, enforcing visitors means losing visitors.
• Trade-off: 
• There's a latency below 1 second to have user data ready to render contents.

Chatfuel:

• Usefulness: 
• Visitors don't need to create accounts, use Facebook accounts to chat.
• Direct chat pop-up in current website page without the need to open new tab to chat. Chatfuel is the best app for integrating Facebook chat in a website as Facebook doesn't provide chat HTML embed for websites. Besides, Chatfuel is even better than other apps for Facebook chats that it is AI-powered, although not yet with powerful AI (doesn't pass Turing test, uses text classification to make responses).
• Trade-off: 
• No trade-off, perfect chat embed!