I don't understand how the whole "heels up/down" thing is still a question. Even my previous types (DHC-6 and -8) had pedals designed so you could actuate brakes or rudder independently. It's poor self awareness/lack of motor skills if you can't keep the toes off the brakes while using the rudder.
To me it all comes down to this: you want to have full control of the airplane in the least amount of time so you can apply corrections should it be needed. I've never experienced any problems on any type by placing my feet heels up on the pedals. And yes, current type is A320