I just tried an image count and there is an item count on my internal, but not an image count. The item count is probably 10% higher than the images that show in Lightroom. Could this be the folders accounting for that variance, or is just that all the pics didn't transfer!
Aperture can handle more file types than Adobe. Might be one reason. The only files I had in Aperture were images files so not an issue.
The only way I could figure out how to do it was go folder by folder, comparing Lightroom to Aperture. In my case, Lightroom was showing 1,331 more images than Aperture. To check, I imported Aperture's Library into Lightroom. Same 1,331 difference. Essentially, those images were in my folders, in Aperture's Library but no preview was available. Tried reconnecting, importing (no as Aperture believed the image was already there).
I spent a lot of time on this as I wanted a clean start. The images missing in Aperture and showing in Lightroom were frequently images I recognized. In many cases there were version exports showing in both but the corresponding master was in Lightroom but not Aperture. Essentially the Library must have been showing a link to an image that Lightroom picked up but Aperture could not.
People have had issues with Aperture's data base since day one. The net is filled with missing files stories. Not to mention many don't know they have missing files. If the preview is missing, as in my case, how does one know. Again, have been using Lightroom as my default DAM and developer for 2 years now. On the DAM side, delighted. I personally don't believe Lightroom's Develop side is all its reputed to be. Yes some sliders have more effect. But the result is a mess. Crank it down to where it looks decent and it's at the same level as Aperture (NR and highlights). The color module (HSM) is primitive. As are local adjustments. It's slow, no matter how much CPU one throws at it.