Ahriman
Tyrant
Academy is 5 science base. Game lasts what, 330 turns on king? So thats 1550 science max (not counting bonuses from buildings).
From that I would say that up until the renaissance, academies are definitely better. Especially when paired with building bonuses.
You're ignoring the opportunity cost. At 1550 science, you're also giving up (say) 660 gold from a trading post on that tile (more since gold is increased by golden ages). Which is, among other things, at least 2 research pacts.