Advantage of using a DialogFragment over simple AlertDialog?

I've read several stackoverflow.com answers, but still don't see the advantage of using a DialogFragment over a simple AlertDialog. I have, apparently, two strategies:

a) use an AlertDialog.Builder to configure an AlertDialog, .create() it, and then .show() it in my Activity (in some button handler), or

b) subclass DialogFragment, write the same AlertDialog-building code in onCreateDialog() (except I just return the .create(), and then, in my Activity, instantiate a DialogFragment, and show it.

The output looks the same.

Either way, I am not using deprecated code -- I am using .show() with both the AlertDialog or the DialogFragment. Is the advantage when I go to another sized device? Or what's the point ...

Thanks for any insights,

Michael