Tarsi
One is cheaper. The other is likelier to get finished. Pick honestly.
The avalanche method attacks the highest interest rate first and costs you the least money. The snowball method clears the smallest balance first and costs you a little more, but pays out a win early.
If your debts are close in size, take the avalanche, because the maths wins and the motivation difference is small. If one balance is small enough to clear in a month or two, take the snowball and buy yourself the momentum.
What matters more than either is making every payment visible. Debt that lives only in a banking app is easy to underestimate, and credit card minimums are designed to keep you comfortable for years.
Track each balance in Tarsi with its rate and due date, log payments against it, and watch the payoff progress. Seeing the curve bend is what keeps the method going.