At the time that I switched, the Hangouts app was having some difficulties of its own. The biggest issue I had with it is that Hangouts would try to upgrade me from an SMS chat to a Hangouts chat with someone, when the recipient was an infrequent or Gmail-only Hangouts user. Google would recognize their number and send Hangouts messages, they wouldn't see the messages on their iOS device because they didn't have a Hangouts app, so to them it would seem like I had stopped responding.