I can lend some thoughts on BM vs 3sphere. Against fair decks that play 3c duals, we're highly favored anyway. Adding more disruption with Blood Moon tends to be win-more than Trinisphere. However, against the unfair combo decks, Blood Moon may not affect them at all; whereas Trinisphere is flat out the best card to have early. Thus, we're putting the conditional disruption (Blood Moon) in the sideboard when we need it and staying with the better disruption in the main.