Hello again,
Thanks so much to everyone for their responses.
The decision is Oxford. As many of you brought up, having a clear idea of why I am doing a PhD was critical. In many ways getting a good job offer really helped bring this to a boil in terms of weighing pros and cons, life plans, relationship issues, financial security, etc. At the end of it, thankfully, the decision to go to Oxford over the job was fairly clear and I doubt that I'll be second guessing myself (at least not for a little while). Moreover, as one of the posters brought up, the job offer may have been less promising than I initially thought; vague assurances over duties, pay, promotion by someone who had not been there very long raised the possibility of getting disappointed in a big way.
Anyways, thanks again for your responses. Let me know if you're going through something similar. Hopefully now I could give some perspective!