Nimzovich-Rossolimo attack, bxc6 or dxc6?

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Bontrager

I hope I named the opening right :)

 

As black I can never decide whether to take with bxc6 or dxc6. Rather than just getting an answer, I would like to know how black's overall strategy changes depending on which pawn that captures? Like, what should I go for after I take with the b pawn or the d pawn?