Which approach is better to copy a list?

[nexusfactor]

Any reason why I should stop using it?

The one time you would not want to use it is when you need a deepcopy in which [:] is a shallow copy.

As the PCC book pointed out, if you use [:], the second list has no effect on the first list, you can add items to the second and it will not be reflected in the first. Is there more that goes on in the deep copy that I'm unaware of?