Oxford DPhil Economic and Social History or Re-Recruit?

I'm a current Canadian undergraduate at a top-30 global uni studying Economics and have an unofficial (verbal, from my prospective supervisor) offer w/full funding from Oxford (University College) to read for a DPhil in Economic and Social History. The doctorate degree will take 3 years to complete.

I have no job offer as of now for post-graduation, as I recruited for MBB summer internships last year and struck out. 

Should I recruit again for MBB FT offers, or should I pursue the DPhil at Oxford? Will getting this DPhil hinder my career prospects or not, and what kind of paths can I pursue with the degree outside of academia?