Re: MBA vs Ph.D
Ask99... most Universities require some form of graduate work before accepting students into a Ph.D. program, although in exceptional cases, I have heard of students getting into a Ph.D. program with only an undergraduate degree. The main admission requirement for many Ph.D. programs is the candidate's aptitude for scholarly research and academic writing, and if these aspects can somehow be illustrated - through prior coursework, industry research, RA positions etc, that generally helps.
The average completion time for a Ph.D. in North America is 4.75 years after a Master's degree, while in Europe, it's around 3 years. The time is primarily determined by the coursework requirement (some Universities require fairly minimal coursework, while others require multiple years of coursework), residency requirement (usually two years), comprehensive examinations (required at most North American institutions), and of course, the availability and helpfulness of a candidate's supervisor and advisory committee.