Back when I started student-teaching, I remember being observed by MTA's then-principal Rabbi Mordechai Spiegelman. During the course of shiur I mispronounced a word. Afterward, when we met, he said to me "If there exists a Steinsaltz edition of the masechet you are teaching (that's how long ago it was), there is no excuse for not pronouncing something properly."
This was a lesson I took to heart, both for myself when preparing and for my students.
I much prefer using Tuvia's gemarot whenever I can. That way, when preparing a Tosafot, my students don't waste time trying to find "bodai" in Jastrow when what they were looking at was "b'vadai." (Ma'aseh she'haya.)
