Flash is also able to produce vector graphics

In fact, no matter what program or tools you use, creativity is your limit here., just that Adobe Illustrator provides a more comprehensive tools and better functionality which let you done more work in less time. Keep in mind that things that can be done in Illustrator can also be done in flash, just that it consumes more time. For vector animation instead, Flash does a better job. There's no ultimate 'tool' in vectoring, just your creativity and imagination.