EDUSWAMI ANSWER
The 1 year MBA is ideal for candidates with some degree of work experience who can then assimilate the concepts much faster and with lesser effort. Apart from the pace, there is little difference between the 1 year and 2 year options in terms of rigour, depth, quality, content, and level of knowledge gained. In fact, the contact hours (i.e. amount of time spent in the classroom) is just about the same between the two in most programs. The learning experience in the shorter version is enhanced by the real life experiences that the students bring to the classroom and the ease of correlating academic concepts with real life settings.
Hence, the odds of a successful switch of function and/or industry are more or less equal between 1 year and 2 year MBA programs.