I love the Romani. Despite the fact that their armies need replacements all the time during a campaign, but they have lots of money and manpower reserves.
Makedonia is my favourite Diadochoi faction: it has powerful elite phalanxes and the like and, contrary to Romani, I can stay with the same army with little replacements for a lot of time, thanks to the fact the AI loves an all out frontal charge against phalanxes. Plus they start from the zero and it's better to build an Empire than to inherit one (one reason I dislike Ptolemaioi and AS).
Arverni is my favourite barbarian faction. It takes some challenge to play them because their infantry is not very exceptional and they're tied in no less than total war. Challenging but fun.
I have never tried KH, Saba, Sauromatae, Saka, Pontos, Hayasdan and do not intend to do it anytime soon.
Factions I dislike: Aedui, because the Arverni COA is cooler (otherwise they are almost identical), Casse, because they are small and their Chariots are bad.
Factions I intend to play in the close future: Sweboz, Getai (very nice infantry and light troops, safe starting position), Pahlava (I'll try a different cavalry commanding scheme), Baktria (good Hellenistic roster).
I just dislike Karthadastim for some mysterious reason. Never got appealed to fight as them, but love to fight against them no matter what is my faction, but mostly with the Romani for the need of it early on.
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