I also recently came across this info when I was searching for Aperture related subject matter. Can't verify if this is true and I know some probably get a heartburn when you mention the authors name but thought I'd copy and paste and provide a link to some of the technical differences between how Aperture and Lightroom work with RAW files (feel free to shoot the messenger as I'm wearing my kevlar protection suite ; ):
Apple Aperture Review
Technical Supremacy
Rich guys think they're cool when they open a raw file in Photoshop's Adobe Camera Raw (ACR), and spend a day jacking it in Photoshop with layers and masks.
We can do the same thing faster in Aperture, and there's a secret. I knew all this, but is became apparent why Aperture is technically better when I jammed the Shadows slider and was able to pull up black shadows that were 8 stops underexposed, with vivid detail.
When we open something in ACR, it's converting the raw data into a raster image that is then processed in Photoshop. If we open the file in 16-bits, all is well. All our adjustments made in ACR are done once, and then we have our 16-bit file to tweak in Photoshop to our heart's content.
By comparison, Aperture never makes any final conversions from the raw data until we do a final export of an edited version. Every adjustment and brush is applied to the virginal raw information just once.
When a raw file is opened in Photoshop's ACR, ACR applies all our white balance, exposure, contrast, black-clip and every setting to the data, and produces a big file from it. Here's the problem with this: we always lose something in this process. Add exposure, and we lose some highlights. Open with whatever black-clip setting, and we lose some shadows.
No matter how much we screw with something in Photoshop with what started off as a raw file, we're losing information as soon as we've converted the raw data into a raster image in ACR. Photoshop can't process raw data: it needs the raster data from ACR, and ACR does all sorts of curve shaping, truncation, redithering, rounding and you name it to convert the 14-bit linear raw data into 16-bit log z-axis data. Photoshop asks you to make final decisions in ACR before you even get to start working in Photoshop with a raw file!
Contrast this to Aperture, which is always working directly from the original raw data. All the settings we apply in Aperture are calculated directly from the raw data, so if we need to add black clipping, highlight compression, sharpening, severe white balance shifts, and add strong shadow recovery as well as burn and dodge, these are all calculated from the original raw data. There is no raw-conversion happening a la ACR before Aperture can read the file; the only conversion from raw happens in Aperture only on export.
Here's an example: we sharpen in ACR as part of the demosaicing, but do arbitrary rotations later Photoshop to fix an unlevel camera. ACR does all sorts of inter-pixel interpolation to demosaic and sharpen our image, and we lose more sharpness when re-interpolating again performing the arbitrary rotate later in Photoshop. With Aperture, the raw data is never touched, so the demosaicing, rotation and sharpening are all calculated in the same conversion sequence from the original data, only on final export.
Aha!