For me its aeon. You get decent T1 land, Great T2 air with mercys, Best T3 land with harbs and shields and GC is also very good if the game ever gets to that stage. The aouras can hover giving you a distinct advantage on water maps.
I see sera used a lot probaly for T1 arty, T1 bommbers, good ACU and isahovs. Anyone else got an opinion on this? nd what faction is used most for ranked? has anyone got any statistics?