I use to only feed my corn snake live, at the time I had one other ball python that ate f/t. I feed the corn snake f/t for the majority of its meals and live only as a "treat." One day the snake didn't get a decent strike on the mouse the mouse started biting the snake. I grabbed a large spoon which was close to me and had to break the mouses neck with the snake curled around it. It wasn't fun and I didn't like having doing it.
To each their own but in my opinion f/t is the way to go. You have people that have always feed live and never had a problem but then you always hear the horror stories or see the pics of snakes all messed up from being feed live. I now have 6 ball pythons 1 boa and 1 corn snake they all eat f/t. Now it wasn't the easiest thing to do to switch them to f/t but it can be done. My suggestion if the snake is over a year old don't offer live again. Give him a week to get use to his place offer him f/t if he doesn't take it leave it in his cage overnight. If the prey is still there when you wake up take it out throw it away and try again later. I do this on an every 4 day cycle till the rat or mouse is gone.
It does take time to switch though and you have to be keep to your guns, the snake will eat when hungry enough. If it is a hatchling then by all means feed it live but something defenseless like a rat pup its first couple of meals and then try to switch to f/t. one last tip i have found it to be easier to get them to take f/t when you do a couple of things. Make sure your meal is warm, ball pythons have heat pits and they can tell if the meal is live or not, simply by the temp they are registering. Scent the room, I let my f/t thaw out in a 5 gal bucket before feeding so the snakes smell the food and start to get ready to eat. And move the prey, I always use tongs to move the f/t prey around this helps them think it is live as suppose to just throwing a dead mouse in the tank.
I have had great success switching ball pythons with the methods listed above. All of my ball pythons came to me as live feeders, and all have been successfully switched. I hope this helps, in the end feed whatever is easiest and most feasible for you. I hope this hopes and good luck