Below are the two images that I worked up in Aperture and Lightroom. The image from Aperture is on top.
They're pretty similar save for saturation and color balance differences. Actually, it's remarkable how similar they look since I didn't compare them during the processing stage.
When I opened those two images in Photoshop to do a little pixel peeping--sorry, I couldn't help it--I was surprised to see funny business going on in a few parts of the the Aperture image (see comparison below). There were some strange artifacts, some funky color blooming, and and overall crunchiness I haven't seen before in an image worked up in Aperture. Definitely not what I was expecting as all my previous tests with Aperture showed its RAW processing quality to be as good as anything else I've seen (save for Nikon Capture NX since I shoot Nikon).
[As a side note, I couldn't find a tool to deal with chromatic aberration in Aperture. It must exist somewhere because this image had a bit of color fringing going on and Aperture took it out automatically somehow.]
I decided to try another image, one that I knew was crazy sharp and would give Aperture a second chance. Perhaps I messed up in my RAW processing of the above image, though I processed it four or five times to see if I could eliminate the crunchiness. Round two would hopefully vindicate Aperture's RAW processing quality. (Please note that I'm using the latest version of Aperture with the RAW Fine Tuning HUD Version 1.1.)
For this second comparison, I chose a portrait from a recent stock assignment, which was shot in a studio with strobes. I followed the same strategy as before and turned off all sharpening in both programs. The exposure in camera was pretty much dead on. I also set a custom white balance in camera with a grey card so there wasn't a whole lot to adjust in the RAW processing stage, just a little contrast and saturation.
Below are the two images with the Aperture image on top and Lightroom image below.
To my eyes, the color's very similar but perhaps there's a little more saturation in the Lightroom image. Doing this test is also a great reminder that not every RAW processor produces the same colors--each processor creates a different look just like individual films. I can't say that I prefer one look over the other at this point. The redness of the subject's skin isn't pilot error. Atom is a professional kayaker who just returned from two weeks of kayaking in sunny southern Mexico right before the photo shoot.