Mayans should have a noticeable advantage. Yes, I know rattans archers and imp skirms eat plumes for breakfast and all that. But Vietnamese don’t really have good answers to eagles and siege rams. Cavalry is average at best and infantry is mediocre without blast furnace.
It’s not a clearly lopsided matchup, but I would almost always take Mayans on that matchup on most standard maps.
Mayans are one of the top civs, but if I pick mayans and my opponent randomly gets vietmamese, I am not that happy.
Rattans do actually much better than arbs vs eagles since they have +1 attack.
Vietmamese have access to good champions and light cav (missing just the +2 attack), which are fine for fighting eagles and raiding. Mayans are more mobile, despite Vietmamese have a gold-free cavalry unit…
Vietmamese can beat mayans easily in direct fight with champions and an anti archer option, with a less gold-intensive army. Also they have superior trash.
Still mayans are just a top civ, so with their superior eco they should have a small advantage, but viets are not that great opponent for them. Raiding in castle should be the key for mayans…
Players are more used to the mayan gameplay, cheap archs+rams or switching to ews is pretty much gg for the vietnamese, if the player has less experience then you can expect the typical rattan vs plums, but that is less likely to happen, rams+ew is the vietnamese combo killer.
If somehow you reach late game with lots of resources then, rattan+cavs or even eles+canons can win you the game but it ain’t that easy.
I think Mayan eagles nice but if Vietnamese produce Elephants its going to be counter both Eagles when archers at back kills plummed archers. I think if Vietnamese wants to win Vietnamese need to choose their units true, if Mayans wants to win Mayans needs to raid and micro a lot.