Smash Bros. for Wii U Features Slightly Better Voice Chat Capability than Mario Kart 8

Well, Nintendo is making positive steps forward on the voice chat front. When playing online you will be able to voice chat with others in the lobby area, on the menu screen, character selection, and after battles. Unfortunately for some, you can’t voice chat during battles, making it extremely comparable to Mario Kart 8. They could really work around this by enabling party chat to always be used system wide at all times, but Nintendo doesn’t seem to want to do that at this time. It’s okay, it won’t stop me from trash talking my fellow ZI staff when I tear them a new one with Ganondorf.

Voice chat will be enabled using the microphone on the GamePad (I would assume headsets also are supported).

Source: Gamnesia