Thread: Muzzle Break Efficiency

What type of MB is the most efficient .
I know that's like asking " How long is a piece of string " but is there one particular type or design that works the best ?
Are some louder than others ?
If my barrel is already threaded for a MB can I just buy and screw on another MB or should they really be fitted and checked at the time of threading to make sure everything is lined up and accurate ?

Ken