that is not a straight forward question since it depends a lot on the car and how you are driving. for instane, is it an automatic, is it a manual, is it an electrohydraulic with automatic clutch, double clutch, dog-shift gearbox, how responsive is the throttle etc. also, are you driving on a loose surface, tarmac, icy conditions? what does the torque curve of the engine look like (for instance, does your car have a whopping big turbo that has to be kept above a certain RPM to have power on tap?)
in an ordinary car: use your right foot. it is likely that this is what you are used to so your right-foot motor skills (pun intended) will be significantly better. if you have tried to brake with your left foot, and you are not used to it, you have no doubt experienced that you will tend to apply too much brake too quickly. and at the other end: if you have a braking system that takes a lot of force and you have grippy tyres, your left foot will probably significantly weaker as well.
if you want to play around with it a bit I can recommend gokarting. gokarting is brilliant for practicing braking with your left foot as most rental gokarts have crap tyres that are real easy to lock up at even modest brake inputs :)
in an ordinary car: use your right foot. it is likely that this is what you are used to so your right-foot motor skills (pun intended) will be significantly better. if you have tried to brake with your left foot, and you are not used to it, you have no doubt experienced that you will tend to apply too much brake too quickly. and at the other end: if you have a braking system that takes a lot of force and you have grippy tyres, your left foot will probably significantly weaker as well.
if you want to play around with it a bit I can recommend gokarting. gokarting is brilliant for practicing braking with your left foot as most rental gokarts have crap tyres that are real easy to lock up at even modest brake inputs :)