If you like Maths/Science then obviously do a BSc.
Maybe you want a bit more high powered career opportunities. Then either do Engineering or econometrics or actuarial studies.
Thats not to say a BSc is crap, its just a bit harder to get a high powered job in. But then, maybe thats not what you want. If you want to find the next cancer fighting drug or something by all means do a BSc.