Ever you which to print your own baners, with the trade of your site, or some baner from ad regie, you have better to insert only one code on your page, which you can drive by an admin. You don't have after to always change your code.

Many Ad regies give you the possibility to manage your banners, so, you'll admin it on their site after.

Details

If you use many scripts, you could have some bug on the number of printing and of stats. So, do at first time the compatibility of your own script.