Most people prefer using a peeler to peel potatoes because it's designed specifically for this purpose and makes the task easier and more efficient. Potato peelers are usually sharper than regular knives, have a swivel head for better control, and a comfortable handle for grip.
However, some people may choose to use a knife to peel potatoes if they don't have a peeler on hand or prefer using a knife for other reasons. If you decide to use a knife, make sure it's sharp, and exercise caution to avoid accidents.
In summary, while both a peeler and a knife can be used to peel potatoes, a peeler is generally the tool of choice due to its design and efficiency.