You can't beat the -33% gold costs for buying units. If you plan ahead and combine it with mercantilism from commerce and big ben, you can buy an entire army in a few turns.
Also, on Immortal+, tier1 tenet -> spies steal technologies twice as fast is too good to be true. I don't know how the game calculates it but it often went from 40 turns left to a minor 15 turns. Plant every spy in different cities of a runaway and you get a new tech every 5-10 turns.
Sure, it's easier to win a war as a tech leader but in BNW, each city you conquer has this stupid science penalty. Your science per turn might be the best in the game but, ohhhh sorry, your techs cost twice as much now for no reason ...
Overall, I'd say Order gives the most happiness though.