From what i observe, the Data science is the latest "hot cake" being sold in the market and clearly the opportunities are far diverse than an MFE ( which traditionally caters to Finance audience ). That said, i would definitely re-iterate what Lyosha mentioned - the DS course these days tend to sell a technology stack to you - and without indepth knowledge of the underlying technology, the benefit from most such courses ( with superficial knowledge ) is going to be short lived.
It might boil down to these criteria -
1) Does Finance intrest you thoroughly ? then MFE.
2) Are you a Phd in Math , stats specifically - then DS. I believe Phd is added plus for MFE, but a Math Phd need not be like a pre-requisite. For DS, I think Math Phd should be must. If you are weak on Core DS technology Stack, and then just a grad in Math, you might not take off in DS.
3) Obviously the avenues for DS are better than MFE, and with the Silicon valley start up bubble, Data analytics is only going to go upwards for next 5 yrs.
Speaking for myself, i am completely for finance, hence shooting for MFE.I am from engineering + programming background, hence I am trying to learn DS basics - cos it gels well with applying the Python,R concepts.