My response is as follows: The various labels can be confusing. The main differences can be found in the manner in which programs respond to a few key questions outlined below. Be careful not to omit any particular category of programs in the earliest stages of your search as hybrid programs are emerging in many places. Also, labels do not always accurately convey the orientation of the program. Here are questions that might be helpful to explore with potential programs targeting professionals in your area:

• First, when do classes occur? Executive MBA programs, Fast-Track and Flexible MBA programs often offer classes on Fridays and Saturdays. Part-Time and Professional MBA programs generally hold classes on weeknights, though some are beginning to experiment with Saturday options.
• Second, what is the profile of the student body? The lines are beginning to blur on this question but generally Executive MBA programs are intended for senior professionals with 10-15 years of work experience. Most Part-Time and Professional MBA programs require a minimum of two or three years of work experience and their student bodies often average five or six years of experience beyond the bachelor’s degree. Flexible and Fast-Track programs sometimes cater to early career professionals and the student body might include a few students who moved straight from an undergraduate program into the MBA program.
• Third, does the program include “residencies,” required international experiences, or capstone projects? Many of these concepts originated in Executive MBA programs and have been adopted by Part-Time and Professional MBA programs. In some cases, especially in Fast-Track MBA programs, the international experiences are optional.
• Fourth, how broad and deep is the curriculum? How long does it take to complete the degree? Naturally, Fast Track programs are among the fastest (think 15-24 months) but the curriculum is often smaller than you might find in other degree programs. Executive MBA programs are often 18 - 20 months from beginning to end. Part-Time and Professional MBA programs can be 30-36 months in duration and usually allow you a bit more room for elective courses. They are more likely to offer tracks or concentrations. Flexible MBA programs often allow students to stretch the degree to 4 or 5 years.