I have both an Echo and a Home. Google Home is able to answer more questions and is a little more versatile. If you use any home automation, you will want to make sure that your hub is compatible with your assistant. Also, Google Home hears the key word much better in a loud room over Echo.
As far as sound, the Google Max has microphones and automatically calculates the acoustics of the room and adjusts the sound. If you have ever listened to music in the corner of a room, you may noticed a muddy sound. Well the Max accounts for this so you get a near perfect sound, regardless of wherever you are in a room.
Since it has not been released, I can't tell you how it sounds. But if it is as good as promised, I think it will be one of the top audio devices in its price range.