The main benefit of the Aperture-to-Lightroom importer is metadata migration, not edit migration. Based on the community answers, it can preserve items such as flags, star ratings, keywords, GPS data, hidden-file status, and face-name tags (mapped into keywords).

If you import only the Aperture Masters folder directly, Lightroom will bring in the image files, but you generally won’t get that Aperture organizational data automatically. So the importer is mainly useful if you relied on Aperture’s cataloging features and want to keep that work.

What it does not do is transfer Aperture adjustments, so your edited looks won’t come across as editable Lightroom settings. In that sense, if you only care about the original files, direct import may be enough. If you want to retain your ratings, keywording, GPS info, and similar library organization, the importer gives you more than a plain file import.