AutoCAD vs. ProEng.
ProE software is not hard to learn. It is just hard to make your model smart. When I first start using ProE, I had to make modification to a model created by some contractors. This was the best experiance you can get, and after a month of working on them, I learn what not to do. If you ever use Proe again, look at the parent/child relationships and the references of the feature you are modifying first. You know what is causing problem before it crashes.