Primogens... sounds very video-gamey, or like the name of a heavy metal band. But the only feel I get from it is "We can't think of anything that describes our game, so we're just going to pick something that we think sounds cool and heavy metal style." Not a name I would pick.
It sounds to me different, in fact is the option I like the most among the others. It brings me to mind the way medieval lords legated their domains to the eldest sons, who kept the title and rights while the youngests had to make career in a monastery
But it's true that for somebody without the slightest clue of what the game is about, maybe it would sound a little "heavymetal-ish". Anyway, personally I think it's the most elegant and "serious-looking" option, with a cool air related to aristocracy and such.
