I'll point on disavantages of some types of chat.

1 - Being VOIP (Voice Internet Protocol, or something like) has the problem of poor (or none) understandability for those individual with first language non-english. Valuable for english speaking individuals but only a mix of sounds for those non english-speakers.

2 - Other type of chat has the problem arising from the fact they don't allow registry of its contents. That don't occurs at "chats" like those supported by this forums. Valuable opinion interchange (threads) are lost when chats are of MIRC of Messenger type.

My best regards,
Ángel