Specifically with their 4.5 in Ar 9 mm barrels?  I'm trying to decide between a ballistic advantage 5.5 in and the radon 4.5 in.  This is going to be for a Ar that will be run supressed 100 % of the time.  What say the people in the know what's better 4.5 or 5.5 and the quality difference between the barrel makers?  Granted I see shorter S better because the subs will I assume quieter out of it.