Their base stats are similar to Dialga and Palkia's (90, 100, 100, 120, 120, 150) but they're distributed differently:
Reshiram's stats:
HP: 100
Atk: 120
Def: 100
Special Atk: 150
Special Def: 120
Speed: 90
Zekrom's is similar, but its physical and special stats are switched around.