Is there any benefit to a tubed phono stage?

Benefit, of course!! Solid states are very good ones as well, but with tubes comes Tube rolling and finding what flavor you like, yeah it costs, and yeah it could take some time and knowledge to find the right tubes, but bottom line just like any preamp you can customize the sound.. Solid state is good but will always sound the same or generally anyway, if its too hard sounding or to soft sounding with your cartridge combo you got no choice but to keep messing with cartridge settings or changing it all together, the tube changing should be cheaper and can be more effective. But I would find one with not too many tubes and this will reduce the issue over going crazy with some 8 tube phono pre or something. Just my opinion, but I have had a few hi regard stand alone Solid states, and Built in pre's in solid state preamps, I listen to mostly hard rock, classic rock, and stuff from the beatles on and just found tubes to be much nicer to balance things out, plus I have capabilities to change the input impeadance for MC which really helps match up the cartridge.

The K&K phono is designed to use the Russian 6N1P tube. NOS versions of this tube are still available for $5 a pop. For $100 you could have a lifetime supply! Tube rolling and tube cost are not an issue with this phono pre.

transistors in general have the characteristic of loosing low level detail and adding odd-ordered harmonics that make the sound harsher.

Once detail is removed and the harmonic structure is tainted, no amount of work downstream will get the music back. So yes, there is a huge reason to use tubes.

The drawbacks: tubes are often noisier and you may have to spend some real cash to get a quiet phono section if you are using low output cartridges. Tubes do need replacement as they wear out.

My advice is to avoid phono sections that use tubes that are out of production and those that use 6DJ8s (which tend to be microphonic). Doing this will avoid a lot of headaches!

I too have the K&K phono stage and would agree with the statement that it's not whether something has tubes in it but, rather, how they are implemented in the overall design. There is nothing noisy or mushy about this phono stage, but there is something ineffable about it's sound that only tubes seem to bring to the party.

The only benefit to a tube phono stage is "fidelity" otherwise it's just a big pain in the ass. I love the sound of my Aesthetix Rhea and I have a friend with an I/O signature which sound's beautiful. Either make music like no SS phono I have ever heard. If you like vinyl, you'll really like vinyl on tubes!
Happy Listening!