These pull in different directions. The La Prima has more torque - 12 Nm versus 8 - and Asetek's industrial build, but it is PC-focused and $200 dearer. The CSL DD 8 is cheaper, works on Xbox as well as PC, and scores higher on our rubric, punching above its price with the 8 Nm Boost Kit PSU. So the Fanatec wins on value, reach and score; the Asetek on torque and build.
If you want into the Asetek world and the extra torque, and you are on PC, the La Prima is the base - its build quality is the draw. If you want the better value, console support, or simply the higher-scoring base for less, the CSL DD 8 is the smarter buy for most people. It comes down to whether Asetek's engineering and 12 Nm outweigh the CSL DD 8's price and reach.