I got Black 2 to follow with my Black version, but also because:
- Black Kyurem... Who cares what Smogon says, Black Kyurem is boss.
- Exclusives. I believe Magby and Heracross are exclusives. Heracross not so much since you can find it in the Hidden Grotto in White 2, but the possibility of finding Heracross in the grass appeals to me. Also Latios and Gible. The only good things White has are Reuniclus and Braviary, and I only really care about Braviary. Not going to get White because of one Pokémon that isn't even a legendary.
- I think Black versions are the true canon of 5th gen.
- The developmental look of Black versions appeals more to me, although the White Opelucid City looks nice.
I never use legendaries, so I don't even know which is which. But of the rest of the version exclusives, the only ones I prefer in Black 2 are Heracross and Lopunny, while White 2 has Braviary, Camerupt, Reuniclus and Lilligant. And I prefer both old Opelucid City and White Treehollow.
Lilligant and Heracross aren't exclusives.