Human communication consists of so much more than just words. Tone, loudness, speed, accent (a hint of the other person maybe not being a native English speaker), all that gets lost in pure text. And even voice calls lose a lot of context like facial mimic or gestures that convey emotions.
IME an n vs. m written discussion in a public forum can be clearer, more productive, and a hell of a lot more accountable than some potential n vs. 1 adversarial corporate firing-squad 'discussion' intended to reinforce whatever policy the n have already decided upon. IMO, much of the benefit of voice over text is likely offset by the latter scenario being real time with potential translation issues.
