Exhaust stud stud

I have used bolts and studs. both worked fine. Preferred method in my opinion is studs as you are assured that 100 percent of the threads are engaged. If I remember correctly the factory exhaust threads were corse thread into the head and fine thread where the nut spins on on.
Half the time I took the exhaust stud out by accident trying to remove the nut. generally I just revealed it and threaded it back in like a bolt.