This is followed by the AUS with its 105mm standard HE rounds The US have by far the best artillery considering it is 105mm air burst
Other things you did not consider is the effectiveness of each factions artillery. The 30 round magazine late war is not really something to consider when discussing choosing factions as there is no other choice besides ARVN late war. It functions the same as the F-4 with the only possible game play difference being the sound it makes when it flies in. When it comes the the A-1 skyraider, it is practically just remodeled napalm. The artillery for the NLF and the PAVN are different, each being effective in different ways. The spooky, not the napalm is replaced by the canberra bomber However if you pick ARVN on a map with attack helicopters, there will be a cobra.
The ARVN do get the attack helicopter, granted it is technically piloted by US pilots.