The Echo has a code you use for different accounts and the Google Home (GH) just uses your voice.
The Echo is really more of a computer interface and has you do the work and the GH is intelligent and far more human in how it does things.
Really love the voice authentication with the GH as it makes so many use cases now possible.
For example, in our home I prefer some of my kids to be unable to lower the AC thermostat. Now I can have some able to when they ask the GH in the kitchen and others are not able to. But no awkward passcodes, etc.
The other is I am fine with guest able to do some things and then others I only want "privileged" users to be able to do. With the Echo it was trivial for people to learn the passcode. Now with the GH I say it and it will work and they say it and it will not.
But everything is like this with the GH versus the Echo. A huge one is the Echo has commands you memorize and the GH you just talk to it like a human.
So a little kid can use the GH as well as a grandma. Kind of like Google Search. Same text box for a 5 year old as a rocket scientist as well as grandma. Exactly how technology should be. Why on earth should we still have to use passcodes?
Amazon needs to replace the foundation of the Echo to have intelligence if they want to be competitive.