Well, in 26″, I love my trail king (rubber queen) with the UST sidewalls. However, the nearest they do in 650b is the apex/protection. By comparison, it appears to be utter bobbins in terms or robustness/reliability. I’ve had two sidewalls fail in as many months. One of them, about a centimetre of bead decided it no longer wanted to be part of the tyre, the second split/cut the sidewall on a bit of man made trail on the south downs. No point me trying them again in my usual Peak District riding spots if they’re proving to be so unreliable.
I’ve currently got 3 bikes running the 26″ ust in 2.2 and 2.4 several times over. If suffered a couple of carcass wobbles which have been warranted but I’ve never had a sidewall let me down on those. Maybe I’ve been unlucky, but at £50 each, I’d have to be bloody stupid to keep trying.