Adobe bought Macromedia, so Flash is being slowly digested into the whole Adobe world. The versions you mentioned are just that - different release versions of the same software.
The choices you need to make are:
1)Do you want to learn to author flash banners yourself or outsource to a designer on an as-needed basis?
2)If you want to do it yourself, do you want to actually learn flash or do you want to buy a tool that doesn't require you to learn or buy the whole thing.
examples:
http://www.bannerdesignerpro.com
http://www.swishzone.com/index.php?area=products