Both should be entered as soon as possible, for the exponentional benefit, right? Just like starting at a site with extra food, or other means of early growth like the pyramids from a scientific leader, can mean that you double your power in the longer run. But both open up a new can of worms, or possibilities actually. Too many. In monarchy and republic, suddenly hills become the most valuable tiles. But they need 12 worker turns to develop. Am I better off using those workers to road ahead for a war, or building settlers instead of workers? Every time I go into republic, I tend to develop my existing cities until I've forgotten to expand at all. When I combine that with going into golden age early, I lose maybe 15-20% shields/food and some gold. Because I don't yet have developed land, variated, I can't controll this explosion of resources, and it annoys me very much.