To be honest there is no general rule to that. On some of my adult sites, I use the animated banners or on others the static ones and it just boils down to what works better for your audience and you can learn it through testing.
Here are some advantages of the still ads:
Low file size
They do not require any plugins for the users to view them
They are not as annoying as the animated ones
Static banners work on mobile devices
And some disadvantages:
They are not as eye catching
Static banners are not interactive