You pretty much have to use a vector program like illustrator or freehand to do anything useful.
Photoshop is not a graphics creation program. Granted, it's a lot easier than using illustrator, but it isn't very useful for creating graphics.
If you're using a modern day vector program, it really doesn't matter which you choose. Freehand or a macromedia product probably integrates much easier with Flash, but illustrator and others work too.