Really doesn't matter, as long as it eats. Only con to live is injury to the snake but that is very rare. No real cons to f/t if it will take it. Kinda according to what is more convienient for you. Yes...once eating live some will not go back to f/t, not all, kinda varies with each individual snake. All my snakes will eat live and 2 will take f/t when offered.
And remember, there are NO stupid questions.