Not mutually exclusive but typically different use cases.

If I am running hundreds/thousands of queries of the kind:

where col1 = ... and col2 = ...

Then the last thing I want to do is continuously dynamic sample the data, because dynamic sampling is not free - it uses resources to do it. I'll look at extended stats to get the best stats I can on that column combination.

Conversely, I cant have stats on *every* possible column combination. But for a data warehouse, where my queries might take minutes to run, I might definitely consider doing a lot of sampling because its still a tiny proporition of the overall run time, and that sampling might handle lots of rare or odd combinations of columns, joins etc.

Hope this helps.