Paying off your smallest debts first gives you a higher sense of achievement because you see the payments you have each month decreasing right away. However, the smallest debts might also have small interest, which means you aren’t incurring too many fees on them.
Paying off your debts with the highest interest doesn’t give you results right away. You might see your balances not going down any because you are only paying the interest back instead of the actual balance of the debt. However, paying off high-interest debt first means you have less money paid in fees in the future.