blueTowel,
You have to assess all these options based on your situation. There is no hard and fast rule on which route to take and it all depends on your job situation and/or your employer.
Let me try to break it down.
1) File under EB3- the dates for EB3 moved radically fast to somewhere around OCT 2012 couple months ago and is not backlogged and is currently at April 11. So if you think there might be a chance that this dates progresses then sure, file under EB3
2) Complete MBA and file under EB2: This depends on what your job requirement asks for. While just having a MBA doesn’t necessarily qualify you for EB2, you might have to work with your employer to make a JD that requires a master’s degree. Keep in mind, if you are working directly with big organization, they usually do not do that. Ideally you will be a Fresh Graduate with 0 yrs of experience and they must prove that you are worth for the job.
3) File EB3 now and port to EB2: This combines both options 1 and 2. This process might involve more money as PERM, i140, lawyer expense is usually NOT refundable. You can try this route but again to port to EB2, your employer must create a JD that requires you to have masters degree.
Think through all these options and depending on your situation and how much flexibility you have, pick one and go with it. I have seen many people in this dilemma and I think it’s pretty common. Some chose one over other so the final decision depends on your situation. Hope that helps.