My tablet with Android 5 has both hangouts and Google Voice. Hangouts has a capability for video calls, and a layout that is a little more indicative of who said what. But when you look at the Hangouts screen, there is a little description under a text message that says something like "Thu 10:15 AM via Google Voice". Which is doing the actual work? It makes you think that you could uninstall Google Voice and just have Hangouts handle all the text & video communications?