When I say XCOM vs XCOM, I mean the original folks vs the reboot.

I enjoy both games but in terms of how they operate, they're very different.

The original had the advantage of sheer numbers, the fact that you can give wacky load outs (all the grenades and nothing else) and the fact that you can really tweak how a turn goes via the action point system.

The new folks however are arguably tougher and individually stronger. With armor that makes them invisible or let them fly they have the advantage in mobility. Not only that but these guys run off relatively more in depth RPG mechanics that can really make em do some crazy stuff.

Round 1: Base teams, filled with rookies in an abandoned city. Starting on opposite ends.

Round 2: Maxed out, elite teams in the same city, starting on opposite ends.

Round 3: Both sides gain access to all of their expansion set technologies and sequels with the original only encompassing tech for all the pixel graphic games while XCOM reboot gets the mech suits from their expansion and everything from their sequel along with that game's expansion.

Bonus round: XCOM spin offs/non turn based strategy games are thrown into the mix as their own faction. So XCOM enforcer, XCOM: Intercepter and The Bureau: XCOM Declassified all team up.

Side limitations/capabilities:

A: Everything in lore is considered canon and can be used.

B: Only game play feats are recognized. For example, if an attack is described in lore as something that can set anything on fire but does not do so in game, it is ignored.