He is saying that that Saba is the hardest....

I disagree with that though. It is true that you face two superpowers from the beginning, and that you do so with the weakest unit roster in the game. However, the invasion route from Egypt is easily guarded (red sea coast) and once you unify Arabia, the distance of the desert serves as a general security advantage. You make decent money, and you have the option of invading Ethiopia within ten years, and India within 20. If you do that, you have a decent empire right off, and you can attack the Egyptians and Selucids from multiple directions, making you more of a danger to them than they are to you. Also, you get the good regional units from India (elephants, Longbowman, and those Infantry guild warriors) and Ethiopia (Swordsmen, elephants) that help you to turn the tide when you do face serious armies. Finally, you get levy hellenic phalanxes from your core provinces (regional mic) and although they are not great compared to other phalanx armies, with a few chevrons experience they can be made to be dangerous. Overall, if you handle your early/mid-game well, I think Saba is challenging, but not desperate.
I personally have had more trouble with Early game Baktria, although they can be made into a powerhouse later. I think that the really hard factions are the ones that start out at war with their neighbors, so my vote goes to the Gauls or the KH. Yes they have great units, and once consolidated they are in a great position for expansion and economic growth, but those factions face desperate times in the early game, and the loss of a single battle can derail your early game dramatically. If you don't cheat, and throw in a house rule or two, Averni/Aduei, and KH are tough, and you might not really be established even fifty years into the game.