black nd white are exactly the same except for minor differences like the view of certain cities, in pokemon black you get to go to Black city, and in pkmn white you get to go to the white forest, also the version exclusive pokemon such as zekrom, reshiram, solosis, gothita, vullaby, rufflet, etc.... but other than that theyre exactly the same.
And the starter you should choose is Snivy he has great speed stats, and hes just amazing.
Hope it helps