What is the determining factor for picking Scientific vs. Economic golden age for the Ant->Exp transition?
For me, it's about having a higher base science rate in order to research as many early tree techs as possible before getting free techs from IP's.
1. Having 4 Golden Age Academies (obviously more is better but not always achievable) with (for example) on average of 3 adjacency each gives a base of 28 science. This doesn't sound like much when the first Exploration techs cost is 500 but it quickly increases with bonuses (specialists, science on scientific buildings etc.).
2. If you don't have this extra science, it will take longer to research Astronomy which in turn slows the acquisition of Observatories. Not by much though.
3. Is having more cities from an Economic Golden Age actually an advantage? The more cities you have at the end of Antiquity, the more of an advantage it could be.
Say you end with 4 cities: moving the capital gives you two free cities, the third will likely cost 200 and the fourth 1,000 (not completely sure on this so apologies if it's way more or less!). So you've saved 1,200ish BUT if they remain Towns, they will contribute gold so you're saving slightly less. Plus, if you specialise them, they provide extra yields.
If you ended the age with 7 cities, the amount of gold you're saving is obviously much higher but.....
4. What's that gold going to be used for? In Exploration, I usually only convert a Town to a City when I have enough gold to immediately buy at least the first available science building. If they're already cities then sure, I can buy the science buildings earlier. But if you take the Economic GA, how may extra science buildings do you need to make up for the loss of GA Academies that will be contributing science from Turn 1?
On a related point, if I read today's update notes correctly, it sounds like Shipbuilding is no longer required for Treasure Fleets/Convoys to spawn, so that could shake up the meta a bit. (Also the Hub Towns nerf and Urban / Mining town buffs! Even fewer cities in the horizon perhaps?)
For fast Science, I'm definitely more inclined towards more Towns, fewer Cities. In Antiquity and Exploration, I take the view that the main point of a city is to have the GA science building for the next age and any unique science buildings/quarters. Sure you need a few cities for producing wonders, units etc. but leaving more as Towns means you can increase the food going to cities and gain more specialists in those cities.