One method saves more money. The other one people actually finish. Here's the real trade-off.
If you have more than one balance to pay off — a credit card, a personal loan, maybe a store card — you'll eventually run into two competing strategies for which one to attack first. Both assume you keep making minimum payments on everything, then throw any extra money at one target balance until it's gone, then roll that payment onto the next one.
The debt avalanche targets whichever balance carries the highest interest rate, regardless of its size. Mathematically, this is always the cheapest way to become debt-free — every dollar of extra payment is neutralizing the most expensive interest charge available, so total interest paid across all debts is minimized. A $1,200 balance at 24% APR gets paid off before a $6,000 balance at 14% APR, even though it takes longer to see the second balance disappear.
The debt snowball ignores interest rate and instead targets whichever balance is smallest in dollar terms. This usually costs more in total interest than the avalanche method — sometimes meaningfully more if the small balance happens to carry a low rate. What it offers instead is a faster first win: knocking out an entire balance in a month or two builds momentum that keeps people paying extra instead of quietly reverting to minimum payments.
Personal finance researchers have found that behavior, not math, is usually the deciding factor in whether someone actually finishes paying off debt. If the avalanche method's slower early progress on multiple fronts causes you to lose motivation and stop paying extra, its interest savings on paper never materialize. The snowball method's quick wins are a deliberate trade of a bit more interest for a much higher chance of finishing.
If your balances carry similar interest rates, the choice barely matters mathematically — pick whichever keeps you motivated. If one balance carries a dramatically higher rate (a 24% store card next to a 9% personal loan, for example), the avalanche method's savings are large enough that it's usually worth the slower early progress. Either way, the biggest lever isn't which balance you pick first — it's how much extra you can consistently put toward debt each month.