These land close: the Sport 9 is $80 cheaper with 9 Nm against the CSL DD 8's 8, and it drops you onto Simagic's 21-bit encoder. The CSL DD 8 answers with Xbox support the Simagic lacks and the wider Fanatec rim ecosystem, punching above its price with the Boost Kit PSU.
So platform leads. On PC and a budget, the Sport 9 edges it on price and torque. If you need Xbox, or you want the Fanatec ecosystem, the CSL DD 8 is the sensible pick and no compromise for the money.