The scenario we will use
Three debts, which we will keep to two in the calculator: a $2,400 store card at 29.9%, a $7,000 card at 22%, and (in the article version) a $14,000 car loan at 6.9%. Budget: $900 a month. These are ordinary numbers — nothing about them is extreme, which is why the result generalizes.
What avalanche does
Avalanche aims everything at the 29.9% store card. It dies in about three months, its minimum rolls into the next target, and the expensive interest never gets a chance to compound. Over the full payoff, the strategy pays a few hundred dollars less than snowball — real money, though not life-changing.
What snowball does
Snowball kills the same small card first here — when the smallest balance is also the highest rate, the strategies agree. They diverge when they disagree: a small 0% promo card vs a large 24% card. Snowball clears the promo and feels great; avalanche keeps grinding at the expensive one and saves the money.
The honest answer
Pick avalanche if you are motivated by efficiency; pick snowball if you need a visible win in the first 60 days. Then automate. The people who fail at payoff orders almost never picked the wrong one — they picked one and then stopped paying attention.