Quote from FXsKaLpEr:
Just dropping in quickly to point something out.
Besides Long Term Capital Management, REFCO had ALL the brightest PhDs and MBAs IN THE WORLD.
Yet, the company and its trading failed miserably.
This says a LOT about the real, practical effectiveness of PhDs and MBA to influence an endeavor towards success.
PhDs and MBAs drove REFCO into the dirt even AFTER an IPO.
Fast.

LMAO
Sam
Soryy retail FX video game player, but If anyone believes a word your saying, then this shows the stupidity of half the members in this community. Refco might of had a few phds and a few mbas, but to say they were the brighest is completely asinine. First of all the brightest PhDs mostly do academic research. Those that wish to move over to the financial community work on WALL STREET. They work for the major financial institutions and hedge funds, not a little broker like Refco. The same with the mbas. Management at Refco throughout the firm was nothing to boast about.
Second of all, Refco's collapse has nothing to do with their trading. Remember, refco is mostly a broker and most of its income comes from it's brokerage activiites. Contrast this to a Wall Street firm that earns large sums from proprietary accounts (not to be confusted with proprietary trading firms----the closest thing skalper will ever see, or most of us for that matter). Instead it had to do with lying and just plain fraud on the behalf of a few executives.
Even worse is the sheer stupidity of these executives. I believe that Bennett honostly believed that by repaying the loan he would get off Scott free. Obviously the guy hasn't read a WSJ, FT, CNBC, or any news communique in the past who knows how many years.
Add to this is the fact that the whole Refco organization hasn't used a fraction of its potential (just look at RTS, the place half of you idolized).
Now for the original poster's question. What degree you decide has to do with your personality and goals. They are very distinct and have almost no overlap. Here are a couple of pointers to consider.
First, do a PhD only if you have a serious desire to do research and teaching. It is a long road---5-7+ years for many of PhDs in the natural sciences, with the better programs often taking longer. While the initial work will be mostly classwork, the bulk of the program will be dedicated to research and some teaching. What Wall Street will look like and what it's needs are in 5-7+ years are anyone's guess. Also, if you are only doing one for the money, chances are you'll never make it (although a lot don't make it regardless of their goals).
While PhDs are hot right now, its no gurantee they'll be hot in the future. While I'd guess structured and exotics are here to stay, the need for PhD's might actually decline as programs get written allowing even MBAs the ability to solve complex programs (and of course nonMBAs as well).
If you are really interested in the quant side of the business and have no desire for research, look into some quant masters programs. Some good one's off the top of my head are U Chicago, CMU, Columbia, Berzerkley, Princeton and NYU (among others). Most are completed in 1 or 1.5 years and are more career oriented. The downside is there is no academic career to fall back on.
Finally, the MBA is a good fit if you are thinking about finance in a broader sense. You can still chose a quantitative path, especially if its from a school like Chicago or MIT. It obviously won't be as rigorous as a PhD but might provide a better balance. If you are interested in sales, M&A, or anything else, its probably a better fit. That being said, the demand for MBAs has definitely fallen in recent years.
Whatever you chose, good luck and focus on what you think is your best fit.