A Bonus Battle is decided by comparing how each slot performs once all bonuses have been opened. To qualify for a win, a slot must first go above its Break Even Line, the total cost of all its bonus buys.
If both slots pass break even, the slot with the higher profit wins.
If neither slot reaches break even, the slot with the smaller loss takes the round.
If both slots end at the same amount, the battle is considered a draw.
These rules keep every battle fair and easy to follow, no matter how volatile the slots are.