The poll is so black and white. How about a grayer option: "limited stacking".
Stacks of Doom aren't very fun, but the AI can simply use dumb brute force to be competitive.
1UPT "looks" more elegant, but the scale of the maps (and other things) within Civ5 aren't really optimal for it and, most importantly, it demands a much greater AI to compete with humans (throw in some chokes and water and the AI is already crippled).
Surely, a system utilizing limited stacking could be designed to base the rest of the game off of. It doesn't even need to be that high, a value of 3 already nearly triples the amount of available space for armies to navigate through and operate (and to "hide" before an assault
). Carpets of Doom become Mats of Doom.