RT seems to extract more detail. At higher ISOs, noise in the RT files is finer grained and less detail is lost. IMO, its noise is less ugly than the noise from LR. I have also found it easier to deal with in Noiseware.

I developed all photos at default settings. For the ISO 100 shots, I then applied sharpening in FastStone in order to reveal as much detail as possible. The LR shot got twice the sharpening of the RT shot. I sharpened the second LR ISO 800 shot in an attempt to pull out more detail, but it is not there.

These differences would be less in downsized images or prints, but RT does seem to produce a better initial file to work with.

ISO 100, Lightroom, sharpened
http://i74.photobucket.com/albums/i258/JeffCharles/fromLR-100LX3sharpened10_cr.jpg
ISO 100, RT, sharpened
http://i74.photobucket.com/albums/i258/JeffCharles/LX3hSLI0100rtsharpened5_cr.jpg
ISO 800, Lightroom
http://i74.photobucket.com/albums/i258/JeffCharles/LX3800fromLR_cr.jpg
ISO 800, Lightroom, sharpened
http://i74.photobucket.com/albums/i258/JeffCharles/LX3800fromLRsharpened10_cr.jpg
ISO 800, RT
http://i74.photobucket.com/albums/i258/JeffCharles/LX3hSLI0800RT_cr-1.jpg
Jeff