Not sure if anybody cares about this, but I thought I'd try to clarify how Google Voice and Hangouts are actually quite different...
GV always uses carrier minutes and requires an active cellular voice account on the phone you're using. It routes all outgoing voice calls through a Google Voice "gateway" or "access" number, and it uses your phones voice plan to do that (i.e. your carrier minutes).
There is a beta of a new version of GV that will change that, and provide an option for true data voice calling, but that's strictly beta and limited for now.
Hangouts Dialer is a VoIP service, and only uses data for voice calling - that data can be your cellular data or wifi...it doesn't care as long as there is a data connection to the internet. Hangouts Dialer is great and works well. It connects with your full contact list and works almost exactly like your phones main dialer. It requires a GV number to work, but never uses carrier minutes, and doesn't require a carrier voice plan.