We know almost nothing about these games. It is far to early to pick one, especially on the legendary alone.
But the legendarys are the most important factor because you can trade for (and then breed) the regular ones you can't get, but you can only get one legendary of each per game.
This isn't 1998.
It still matters because most people won't give up their only Xerneas for a Yveltal (and Vice Versa). --- Camelot asked for your support of Golden Sun 4! http://ipetitions.com/petition/operation-sunrise/ "Why? Because of... DESTINY? PAH ha ha!" - Basilio