There was also an aerial version of the Browning .30cal mg with a faster ROF.
http://browningmgs.com/AirGunnery/01_50cal.htm
And who's arguing? I love this stuff!
The US Army made this very decision when they dropped the M14 and replaced it with the M16.
You can carry more rounds for any set amount of weight with the smaller cartridges.
But if I had a rickshaw pulled by one of my subjects I'd go big bore all day long.