I don't know but if you have money to spare, get both! ; )
There's not much difference in Black & White(and they both have like 5~6 exclusive Pokemon for each version).
I decide to go with White because Iris is 8th Gym Leader in White and Zekrom looks cool! ^^
P.S. Dragon/Electric is Zekrom and he's in White and Dragon/Fire is Reshiram and he's in Black, so if you want Zekrom, you should get White like I did! :)