at your age i'd be more inclined to be thinking along the lines of the 1.6 Fiesta Zetec S.

The insurance will be expensive for them both at your age, but the Zetec S will be considerably cheaper to insure than the ST150!

A bit of a 'leftfield' choice for you would be the 1.7L Puma, these are a very good handling cars.
I've had one myself and couldn't beleive just how good they go and handle!