Hey guys, I can perhaps give some perspective from the "other side". I have worked in an S&T role for almost three years, and have in this time been part of hiring MBAs as interns as well as full time employees. In my experience, the school you go to really matters in so far as the relationships it has with the institutions that come to hire. Beyond that the actual content of the MBA program does not matter as much, but of course if you say you had an MBA with a finance focus, you would be expected to know a great deal more.
My own motivation to do an MBA as some point is driven more by a need to seek an alternative career at some point, but monetarily it is not the greatest decision to take. After working for two years, you can generally beat whatever an MBA new-hire expects to make in his first year. So as such if you can get in without an MBA, that's probably the better option !
Finally on the distinction between "s" and "t", it really depends on how you fit into one or the other, and I have seen so much movement between the two that for all practical purposes morphing from one to the other isn't all that hard later if that's what you really wish to do.
As a final note, of all the people I work with, barely ten per cent are MBAs, maybe a quarter or so have degrees like the MSc in finance,so the majority have studied in unrelated fields.