Often communicated wryly, the usual answer to this perennial question is that it is better to learn from other people’s.
But is it?
What exactly are we comparing? We can reason that since it is not good to make mistakes it must be preferable to avoid making them. And having learnt the relevant lesson from similar mistakes made by other people, we can apply that lesson and thus avoid making the mistake, avoid suffering, and avoid causing more of whatever type of damage they caused. As far as that goes, sure. But it doesn’t go especially far. In fact it’s rather trite. Everybody makes mistakes. We have mistakes of our own that we can learn from. Should we seriously prefer to think about other people’s and learn from those instead?
Another comparison might be to consider what is more useful. Is it more useful to learn from someone else’s mistake while not learning from one of our own, or to learn from one of our own while not learning from someone else’s? Personally I’d argue that to improve our mental act it’s probably going to be more useful to learn from our own mistake than from another person’s.