The avalanche is mathematically optimal — it minimises total interest paid and shortens the payoff timeline. For borrowers who can stick with a long-term plan without early wins, it is the rational choice.
The downside is motivational: a large high-rate balance may take many months to disappear, with no visible progress. Pairing the method with a clear payoff calendar and milestones helps maintain commitment.
Same example: CHF 15k at 18% is attacked first; once cleared, payments roll to CHF 2k at 12%, then CHF 8k at 6%. Total interest is lower than the snowball path.