Let's make a synopsis. Here are the main points who support my opinion that Seleucids should be chosen instead of the Lagids. Of course, Lagids is the only serious competitor of Seleucids, since other options (e.g. Dacia, Lusotania etc.) are proposed because of personal preferences and nationalistic views than common logic.
1.
Faction diversity: Seleucids are absolutely more variable, since they have greek, iranean and mesopotamean influences, in contrast to the Ptolemies, whose egyptian culture concerned only some pitiful levies and isolate villages.
2.
Political status: Seleucids were, doubtlesly, the superpower in 270 B.C., despire the fact that Lagids were also a calcuable faction.
3.
Animosity with Rome: Seleucids resisted, not very successfully, to the roman expansion, while Ptolemies were Rome's puppy, since the 2nd century.
4.
Starting position: Egypt's position is ridiculously easy, with only one frontier (Libya was never famous for expansionism) and rich lands. Seleucids are already a great empire, but with rebellous regions and not nat all friendly neighbours, providing the task to avoid a catastrophe and resurrect the achaemenid empire!
Reasons that Egypt may be playable:
1.
Cleopatra : Unfortunately, Cleopatra is quite famous (which means more money), but I don't think that it is a major factor.
2.
Mummy returns: If CA doesn't keep her promise of historically accurate depiction of the Ptolemies, but I trust CA, don't you?