"Video Call" is obviously more limited. If one party has no webcam, there's no Video Call option. If one party doesn't want to broadcast their webcam, or their microphone, video call isn't an option. And yet the new Messenger discards the basic webcam features. It's video call or nothing. I have nothing against Video Calls, and use the feature from time to time. But I use the basic webcam capabilities more.
It's not a bug. It's not an accidental omission. It's a deliberate decision by Microsoft: the new Messenger will have only one webcam mode, and it's Video Call. The company claims that by concentrating on one webcam mode they can make it better. Apparently the picture quality is improved."
Why not just use a mic icon if you have sound only? Yahoo, tinychat ect let the users use any audio, visual or text chat they like and it all works fine from adsl 2+ to 56k, 1 on 1 or groups.