This is a value-versus-torque call inside Fanatec. The CSL DD 8 is the cheaper base and scores a touch higher on our rubric, helped by broad compatibility - it works on Xbox as well as PC and punches above its price with the 8 Nm Boost Kit PSU. The ClubSport DD 12 answers with 3 Nm more torque and a sturdier chassis, the natural upgrade buy when you want proper mid-tier grunt.
So if you are on a budget, or you need Xbox, the CSL DD 8 is the smart pick and no compromise for the money. Step up to the ClubSport DD 12 if you specifically want the extra torque and the better build and you are happy inside a more PC-focused setup. Both share the Fanatec ecosystem, so your rims carry across either way.