It's very light compared to a musket, I'll give you that. And it even looks impressive.
But it will always get defeated by muntions armour (mass produced plate for common soldiers which muskets scoff at), and it has about comparable range to a good 17th c. musket at best, and worse than the crossbows that the Spanish also widely used at the time.
Actually give one a nice metal tip (a good needle bodkin with good iron or steel) and an Atlatl thrown javelin will out penetrate pretty much anything it can hit, and it's a lot more traumatic than getting hit by an Arquebus ball (think about it, five foot bit of wood sticking out of you or a bullet wound, which is going to freak you out more?) and better for use against cavalry, (along with Bolas.) It does take a bit of training to use though, like pretty much anything else.
But yeah, the Arquebus and later musket are the all around better choice for warfare. The Atlatl is just a much nastier weapon than people usually give it credit for being, and munitions armor wasn't as commonly used in Mesoamerica, (speaking from first and second hand experience, the heat and humidity make it really uncomfortable to wear Munitions armor, and it's padding, when you're active in this sort of climate.)
Of course, most of Cortez men were Rodeleros, so there goes that firepower advantage, and a Macuahuitl or Tepoztopilli is a pretty solid threat as well, but something I'd have to get together with the guys and test, while a Cuauhchimalli ought to be close enough to a buckler to be a non-issue.
It's really too bad I'm not still an Anthropology or History major. I could've used that for my Bachelor's thesis. But a guy with an AA in Engineering (and a trained draftsman) working on getting a Bachelors in Anthropology isn't that weird is it?
The last part was a bit of a joke. Wasn't seriously thinking the number of human sacrifices in a given year would have actually had demographic implications.
Everything has demographic implications.
Isn't comparing hanging, a punishment, to a religious sacrifice misleading? It's not like the Aztecs had a liberal penal code...
It's a good measure of the scale of it, especially when you're considering that the Tripple Alliance's domain had something like twice the population of Iberia, (Denevan's "consensus count" of 1976 says 15 million in the Aztec empire, versus a known population of ~7.5 million in spain and portugal, said consensus count is also low due to current knowledge, but close enough in Mesoamerica.)
Add in that there's legitimately fewer crimes worthy of execution (you can't steal livestock as much, heresy is noticeably harder to commit, and there's no royal forrest to trespass in,) and that you've got a better fed population (who are thus less likely to steal) you've got what in all likelihood is a much lower crime rate.