Skype or Zoom. I only use Google Hangouts on occasions.

I prefer neither of these because I had issues in the past with both, and so wechat and whatsapp are my preferences.

Texting 

Many program hosts in a live show prefer to use Skype to connect guests speaking out of studio. 

However, supposing Google Hangout can be used in collaboration with some other programs and applications  you may never understate the potential of Google Hangout. I still  look forward to a better software by Google. I am a lifetime supporter of Google.