If you’re looking for some definitive answer about which tool is better, look elsewhere. The more I work with both tools, the less decided I am one way or another. The only real negative I have right now about a particular tool is that Aperture 3 has some performance issues. It will on occasion blank out the monitor – everything goes dark and then the image comes back? Sometimes the processing just takes a long time. Now I don’t have a beefy iMac, quite the contrary, it’s an old Intel dual core with only 2gb of RAM. Most of the time it does fine but when it doesn’t well you know how that goes. Lightroom does not have performance issues. It processes the Raw files faster and renders faster than Aperture.
The UI in Aperture is probably more intuitive than Lightroom but I don’t see either tool being difficult to work with or hard to learn. I do like the Plug-in Manager in Lightroom, that’s a nice feature and makes it easy to configure the plug-ins. I agree with other user’s who have reported their dislike of the Faces and Places feature in Aperture. To me those features seem out of place in and just get in my way.
So I will keep writing about my experiences with the tools until at some point there is a clear winner that gets me to use them all of the time. Until then I’ll continue to use both tools and enjoying the results.