Persia
Persia's advantages are: Longer Golden Ages, Extra movement, Satrap's Courts, and Immortals
1. Longer Golden Ages. Even without extra bonuses, this means that, provided you keep happiness at maximum, and with clever use of Great Artists, you will enjoy huge benefits. The Louvre, Taj Mahal and LToP all help immensely, and are all get-able on Deity. With CI and/or Universal Suffrage, this goes out of control. The extra culture, hammers and gold you will make in these periods, even with the gaps, will add up across the whole game to a huge amount. UA rating = 7
2. Extra movement. How effective this UA becomes is only contingent on how long you can stretch those GAs out. But in an average game, you will enjoy at least a few of these, and if they are only 10 turns long, it means that for at least 10% of the game your units have +1 movement (assuming a sub-T300 finish, not unreasonable). But this 10% could very easily be 50-60% or more, and if you want to push the military, then this mobility factor truly crushes the AI, who is already out-manoeuvred. I've played DomV as Persia and creamed the opposition, and have seen the benefit even when going peaceful, like I did in DCL #3. Workers with 1 extra move get the job done quicker. Prophets get to where they're needed to prophesise a lot quicker too. UA rating = 4/5.
3. Satrap's Courts. +1 gold and +2 happiness per city is very nice whether you go Tall or Wide, Peaceful or Warring. UB rating = 2/5
4. Immortals. Spearmen that heal at double-rate deserve a rating of 2/5, and it would be 5/5 if, like Impis, they upgraded to Riflemen.
Civ rating = 15