Personally, i think, that TEC Loyalists and Rebels are fairly different, Loyalists being ultra-defensive and Rebels getting their TAR/Pirate/free reinforcements stuff. Especially TAR makes game for Rebels much different to Loyalists. Then, it seems, from the description, much thought was put into Vasari Loyalists, they seem fairly unique and interesting - to my pleasure. I would guess and put money on it, that these subfactions were first to be "invented". Then the others followed. Especially Advent seem to me not really that developed, but maybe its because i am not Advent player/unfamiliar with their stuff.