Neither one is betten than the other. It is 100% your choice. Here are the differances.
POKEMON BLACK VERSION
Opelucid City is technologycal
You have Black City east of Nmbasa City
You fight Drayden instead of Iris as 8th Gym Leader
Some Pokemon are exclusive to this version (Cottonee, Whimsicott, etc.)
Reshiram is the signature Legendary
Tornadus is catchable
POKEMON WHITE VERSION (I have this one)
Opelucid City is old and historic
You have White Forest instead of Black City east of Nibasa City
You fight Iris instead of Drayden as 8th Gym Leader
Some Pokemon are exclusive to this version (Petilil, Lilligant, etc.)
Zekrom is the signatre Legendary
Thundurus is catchable
Iris and Drayden have the same Pokemon and don't vary in any way.