I have heard positive remarks about Oxford's Masters in financial engineering. There will be opportunities in investment banking, hedge funds, and private equity post-graduation, although most will come from the UK and Europe. This is not to say that you could not transition back to the US, but your network will be in the UK.
With regards to whether you should pursue this degree or an MBA, the programs are very different. An MBA focuses on more broad managerial curriculum.
If you do enroll in a Master's program, your chances at an MBA will not be hindered, although you will need to stress in your application why you want to pursue an MBA after already having received a Master's degree.
Hope this was of help.
Conrad and the Stacy Blackman
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