I initially started using Photoshop (PS) and Illustrator (AI) (can't remember what version, but it was in 1999). I stopped using them because I didn't think they were user-friendly, especially Illustrator, for someone knew to using graphics applications. Then I started using Fireworks because it was easier to create vector graphics.
Then I went back to PS/AI a few years ago because of Fireworks' limitations. I currently alternate between PS/AI and Fireworks CS4. Which app I use depends on what I'm wanting to do and how quickly I want to do it.
You'll also have to consider the cost of the apps, whether they're purchased individually or as a package. If you think you'll be using different apps then plucking down the dough for a package would be more cost-effective. I currently have Adobe Web Premium CS4 Upgrade.