Glider
Captain
The AAF liked the 50BMG because it allowed for 6-8 guns with a lot of ammo which enabled the pilot with not great gunnery skills more opportunity to get hits. The USN came around to the point of view that the 20 MM cannon would make a better armament package. Perhaps their POV was influenced by possibly more emphasis on gunnery skills in USN pilot training. Just my guess. The AAF's and USN's opinions were stated in the "Report of the Joint Fighter Conference, 1944."
Going from memory the main arguement for the Navy wanting 20m was because they could do the same amount of damage in a shorter period of time with 4 x 20mm than 6 x HMG. An important point if the enemy is heading for a carrier which can be put out of action with one hit, resulting in you starting to remember the ditching instructions