Logic is for the Music Producer, Mixer, Musician, etc. It's a package that does everything at super high level and that can be expanded with software (VST plugins etc). Basically: it's used for a huge part of the music that gets released. It comes with a huge load of sounds, loops, etc. This program has been around for ages and can be considered to be at the top of it's kind. Other options would be programs like Cubase from Steinberg, Ableton Live & Sony Acid Pro. Each have their own advantages and disadvantages.
I haven't worked with Adobe Audition, but it seems to me it's more a music-editing program. Not aimed at writing, producing, etc. A bit like Protools used to be (Protools is now way more versatile though)...
Sooooo...It depends on what you want to do. If you want to compose music, create sounds, work with sampling, record midi as well as audio, then Logic Pro is the way to go. The price of the package can be called "ridiculously low"! You get someting amazing for a few hundred bucks.
-Xander