hsong1:
Thank you for your question regarding some of InstallShield's products. I'm not terribly familiar with Express and vBuild (don't tell my boss ), but one thing I can tell you is that DevStudio 9.0 combines the features available in Developer 8.0 and Professional, plus added features such as an MSI/MST comparison tool and a new Export Component Wizard, which allows you to break off components and convert them into merge modules.
If you're looking to upgrade, I would recommend DevStudio 9.0. Please let us know if you have any other questions.