I refer to https://xgboost.readthedocs.io/en/latest/tutorials/param_tuning.html
The page says that “there are two ways to improve [the model]” which depends on what you are trying to improve:
Firstly:
If you care only about the overall performance metric (AUC) of your prediction
Secondly:
If you care about predicting the right probability
What is the difference in these cases? When would you prefer the one over the other?