I just got a 2007 Ninja (hope to post pics soon). It's my first bike and I am slowly learning the handling, braking, etc... I got it because of lower cost and lighter weight.
So I guess it's up to your budget and what you can handle. THe Ninja is lighter, less expensive and has a higher seat height (which can be lowered).
The Blast - heavier, cost more, but larger engine and lower seat height. In fact, both stock heights are lower than the Ninja.
Sit on them both and see how each bike "fits" you.