Well ... some folks would consider me a salmon swimming upstream against the current ... it seems we see more than a few Aperture users opting for Lr, I seem to be the exception ... After having used Lightroom since the very first puplic beta of v1 ... in April, I moved my entire workflow to Aperture 3.
There are some things that the Lightroom Develop module (which is the same thing as ACR in Ps) that I wish Aperture could do ... but I create a lot of book/albums and slideshows in the course of a year and I was being crushed by a mountain of derivative files that needed to be exported for use in other apps becuase, as I said, the slideshow and book capabilities of Lr leave a lot to be desired.
In the end, for pure RAW processing, using Lightroom and ACR is the same result ... only a different UI. Though the beauty of working in Lr and Aperture vs using Ps for each and every image, batch processing is much easier, and any adjustments you make are completely non destructive and are not applied until you export the images. Adjustments made to images in ACR are also non-destructive until you "open" the image into Ps proper ...
Since I was already doing two-thirds of my work in Aperture already, back in March I decided to do a six week test working solely in Aperture from import to final client export (though I do use Ps for images that require that level of attention) ... by mid-April, I made my decision ... with the announcement by Adobe in May for the CC subscription model only ... it confirmed my decision to move to Aperture was sound ... I still use PsCS6 ... but there will be no CC in my future ...
The simple answer is that both Aperture and Lightroom will do what you need. Personally, I believe Lightroom has a more powerful RAW engine, but Aperture is more elegant. Since you own iPhoto, my suggestion is Aperture, you'll be more at home and it can access Photoshop CS5 if you need it. Lightroom is ok, but I think for your needs, Sculpture photography and the such, Aperture is better.
Based on your brief requirements statement, Aperture is the way to proceed. I've used both Aperture and LR extensively, and Aperture is by far the better software for managing photos.
At the moment, LR might have a leg up regarding processing of RAW photos. But since you have CS5 you have the same RAW processing engine that's used in LR. One caveat--CS5 and it's version of ACR will probably not see updates to accomodate new cameras. There's ways around that (e.g., DNG) but they are a pain. OTOH, Aperture relies on updates to the OSX system to enable processing of images from new cameras, so it will likely support any new camera you might acquire in the future (they can be slow about it, though).
Aperture offers much more than LR when it comes to managing and cataloging photos. IMO, LR is a lousy system for asset management. It is dependent on a folder-based system, has fewer metadata capabilties than Aperture, and the LR developers seem more focused on the RAW processing aspects of their application. As a result many features essential for good photo management have been neglected and some bugs in that area have been around for literally years.
If "the best managment software for my photos" is your primary objective, go with Aperture. But be sure to put in some time understanding it's asset management capabilities before you get too far into it.
BTW, I agree with Butch about a lot of things, but Peter Krogh's The DAM book isn't one of them. I found Krogh's approach way too complicated for what I do (and I shoot over 200,000 images a year), and he is still basing his system for archival storage on optical media, at least based on a quick look of the latest version on-line. I can't recommend it, but see for yourself by exploring the book on-line.
I'm sure I've already posted this on this discussion but here it is again, updated for LR 5.
It's what I think is the most comprehensive list cpmparing LR and Aperture. I personnally used both extensively.
Although I like ButchM's discription better then what I wrote here, this may have more total information.
I had the same question and ended up going with LR. There is no RIGHT answer to this question....it's really depends on a lot of individual usage factors. As I read LR product reviews that really clinched it for me.
I think both are equally equipped to do the job. It's really more of a preference, but the reviews are helpful.