OK, after yesterday, I went out , shot an image with my Pentax *ist, came back i and loaded the image 4 times, in Aperture, in iPhoto, in Raw Developer, in Canmera Raw, R3.7, (Photoshop CS2).
I did no editing work on the raw file and used default settings for the import. The files were then converted and exported to as tiff files, imported into photoshop, a second time for the CR import and then exported as a png. I selected a small section of the picture that has both a sunset, a cell tower a chimney and parts of three different trees and shadow. The results are below.
Photoshop CS2 CR3.7 import
Raw Developer import
The Aperture/iPhoto images are pretty much identical, (not surprising since Apple built the processor into the OS. It makes sense that they'd decode with the same software in both programs. If you look at the tree in the foreground, bottom left, in the aperture/iphoto image the trunk appears to have light coming through it, in five places right beside the house chimney.
The RD and CR3.7 images show the tree the way it looked through the viewfinder. The CR and RD images have a bit more punch and therefor show a bit more blush under the clouds, but I assume that could be corrected in post processing. IN terms of accuracy, the actual portrayal of what i saw in the viefinder, I have to judge both the RAW developer and Photoshop Raw Processors superior to the Apple processing engine. At double magnification in Photoshop the CR3.7 image appeared to be a little bit cleaner than the Raw Developer image although since the difference doens't show at 100% mag, I'm not sure if that means anything other than that photoshop enlarges it's own files better than it does someone else's.
This is probably as much time as I want to put into it. But from my results. If there is any good news at all it's that iPhoto doesn't alter the Raw files it imports. If you export the raw file to a folder and then process in Photoshop, you get the cataloguing benefits of iPhoto and the better CR processing engine. However it's disappointing that the image quality is so easily demonstrated to be inferior in the Aperture/iPhoto imports. For those who don't want to pay photoshop money for quality Raw file importing RAW developer (availble as free trial download from the Apple website) is avery close second to Camera Raw. If you check out the cell tower and the crown of the tree slighty visible above the roofline of the house, just to the right of the cell tower, you'll see the Photoshop image is a little cleaner than the RD image.
It looks to me that Aperture is basicly an improved replacement for iPhoto, not competition for photoshop if you insist on maximum image quality. And when you consider the HDR images I do three or four times a year and the other stuff Photoshop does that Aperture doesn't do, I'm guessing Photoshop is going to be on my computer for a while yet.