Aztecs for a number of reasons. Their UA is amazing for warmongering and raging barbs, allowing you to fill out the honor and tradition tree, shortly after reaching renaissance. If you can secure a couple camps to farm, I've seen up to averages of 40 and 60 culture per turn off of 3 camps. Tons of culture and gold everywhere when everyone dows you, after burning India's last city to the ground.
Their UB allows for awesome growth potential. Keeping you in the science game to compete with runaways. Who doesn't love a tall cap running max specialists?
Their UU is surprisingly impressive if you build them properly. The 3 rough promotions to further multiply off of jungles and forests, +25 heal coupled with March and double attack is amazing. The hard part is getting them to gunpowder before the AI dispatches them. I like to keep them farming barbs, 6-8 of them. Until I tech gunpowder, then with my full honor tree I upgrade them so deadly rough terrain double bonus gunpowder units. Then the XP building begins.
They compete on Deity. Warmongering and receiving culture from multiple different wars is really fun. I've filled out Tradition, the right side of Liberty, Honor and half of Rationalism before Tenets.
Aztecs are my go to, because I find with more culture anything is possible. Early Peity coupled with Tradition. Commerce builds. Floating Gardens for science wins. But all routes to victory are paved by war, and that's my play style.
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