Boros Dwarves is an even more aggressive go-wide deck than we are, packing cheap equipment and creatures like Dwarven Mauler and Warden of the Inner Sky, so Split Up is excellent at resetting the board if we fall behind on the exchange. Burst Lightning's 2 damage struggles to keep up with their equipped, buffed creatures (Leyline Axe and Dragonfire Blade both pump toughness), making it a weaker removal option here than a sweeper. This is a race matchup where both decks are trying to go over the top of each other, so prioritize proactive plays and only bring in reactive answers where they clearly outperform what's leaving.