they are not that great in muddy conditions as they just clog
Riding in the wrong sort of mud...
Thetford is mostly sand, so no chance of anything clogging there. I guess it depends on if you want tyres specific to a race, or just a decent, fast all-rounder.
Possibly the older version, or the cheapo ones.
@Howard wasn't too impressed with some Schwalbes he had, but I forget what they were.