I am still shooting an X-T10 (X-Trans 2), and experiments processing the same pictures with and without the Iridient plug-in have convinced me that for fine detail, it is definitely a little better than LR.
I don't do any sharpening with X-Transformer, because you can't undo it and I'd rather judge each shot on its merits. I just convert to DNG and do very basic processing in LR before exporting as a Smart Object to PS. which is where any sharpening is done, usually with Smart Sharpen and a mask if needed. For certain textures, such as rough stone, I've found it's possible to get more detail in PS from the files that have been processed with X-Transformer, without having to sharpen them to the point where artefacts start to appear. However, there are not many shots where the difference is important to me. YMMV, of course.
I'm told the difference with X-Trans 3 files is not as pronounced, although I've yet to test that for myself.