ive gone back and forth on this. at first i fed live because its all i knew and could get. then tried f/t and some would take it and some wouldnt. with the ones that wouldnt, i tried several times and several different tricks to get them to eat f/t but they wouldnt and then as soon as i introduced live back to them they ate no problem. now that ive found a rodent breeder near me instead of having to buy from the ahem "pet store", i feed only live. i just make sure to watch every single feeding to make sure that the snake isnt being bitten or scratched and will hold the prey's mouth until it is dead and then move onto the next. IMO that is responsible because im making sure the snake is not hurt and that it is feeding the same way its ancestors have been feeding since who knows when.
the problem here is that sometimes the prey isnt thawed properly and if its too cold, and maybe too warm but im unsure, it can cause regurgitation which is in most cases bad for the snakes health. at least this is all just my understanding of it.