Over the years I've audited a lot of math classes and tried various ways of taking notes.

I've found that live-TeXing lets me keep half my attention at best on the lecture. The people I've talked to about it agree. Also, when the professor requests for the class to be transcribed, the live-TeXing duty is rotated among the students as to not unduly impose on one of us.

I eventually gave up and moved to taking notes with an iPad and an Apple pencil, which has the quickness of handwritten notes, and the availability of digitized notes -- if I'm looking for something I can usually find it pretty quickly by navigating to the class and the (labeled) lectures.

Of course if live-TeXing works for someone, more power to them!