What's the difference?

What’s the difference between flash 4 and flash 5???

That is a tall order of a question. There are numerous differences from the a/s language to design tools, to the panel layout. Far too many to really cover in a post.

If you’re asking if it’s worth it to upgrade… I’d say yes. Flash 5.0 is far more intuitive than the previous versions… and is far more feature rich.