In terms of academic rigor, from what I know the part-time programs tend to be more similar to full-time programs (the curricula is very similar if not identical at some schools - it's just spread out over a longer period). Executive MBA programs tend to have a different curricula than full-time or part-time programs - they are known for being softer on the analytical/numbers side, and heavier on management type courses. Also, part-time tends to meet on weekdays, and exec programs meet on weekends (where more students fly in, so it's not as "local" as part-time programs). Part-time tends to have a wider age distribution - a good mix of young and older, whereas executive programs tend to have a narrower age distro (mostly mid career folks in their mid 30s to late 40s).
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