UCSB's Campus Point
Aperture has features that just do not exist in iPhoto, I already talked about Loupe. Three others are comparison, light table and stacks. There are many more feature but these are the ones I found while trolling around the interface.
Comparison does what it says it does, it lets you compare two photos and choose the better. I tried using it for some photos but my processor was either too slow or I just did not understand how it works. It would also serve me better if I took, say, six photos of a particular subject and wanted to the best of the six. And I am just not there yet.
Light table is a really neat feature without any designated purpose. It allows one to pull photos out onto a virtual table and move them around as if they were on a table. They can be resized, rotated and pulled forward or back. I think the initial purpose was to do mock-ups of publications, I think it would work great in designing posters. The results can be printed (on a home printer) or saved to a PDF and sent to a poster printer service. Once I get the inspiration I plan on using it to design a poster for my dorm lounge.
I now desire a much larger screen.
Stacks are a feature that would make HDR processing in iPhoto so much easier. Stacks gathers up the selected photos and presents them as a single photo. The photo shown on top can be selected from the group. For HDR this would let me stack together the photos to process, export the component RAW files to Photomatix, process them and send the result back to the top of the stack. So in one Stack I could have the result and the source RAW files.
This is compared to iPhoto where I have the final HDR image amid a sea of slightly varying RAWs.
There are more features of Aperture that I probably missed. If I missed them it is because I don’t feel that I need their function or I am blindly unaware that they exist.
Walk the Grass 