I have read about exchanging bishops for knights and inactive for active bishops. I still don't know how to decide when both sides' bishops are seemingly equally active. For instance, I have read that in the London system, Black should try to exchanging black-squared bishops because White's supports White's key target e5. What about the following position (white to move)?
White could try exchanging light-squared bishops with Bc4. Black would have to exchange, keep the tension, or do e6 and have his bishop trapped behind this pawn. If Black keeps the tension, it would be up to White to decide whether to also wait or exchange? Whom would benefit the exchange? Both bishops have the same open diagonal, the main difference to me is that Black's point toward White's king and not the other way around, but in the London system Black is advice to exchange his bishop, that targets White's king.