Torque and price both point one way here: the R9 V3 is $100 cheaper and gives you 9 Nm against the CSL DD's 5, and it scores higher on our rubric to boot. Purely as a PC base, it is the better buy, and that is not a close call. It proved that 9 Nm and PC-only could compete with Fanatec on price and beat it on the upgrade ladder, and this pairing is that argument in miniature.
The CSL DD's answer is compatibility, and it is a real one. Where the R9 V3 is PC-only, the CSL DD works on Xbox too, and it plugs into the widest quick-release rim catalogue in the business. If you are on console, or you already own Fanatec wheels, the MOZA's price advantage does not help you - you need the platform the Fanatec gives you. That is what its extra $100 is really buying: reach, not torque.
One caveat if you do go CSL DD: its 5 Nm is the floor, not the ceiling, and most reviewers will tell you the Boost Kit is the upgrade to get - the jump in detail and authority is bigger than the price difference suggests. Factor that in, because a CSL DD that stays at 5 Nm gives up a lot of ground to a 9 Nm R9 V3. On PC I would take the MOZA; on Xbox or inside the Fanatec world, the CSL DD plus Boost Kit is the sensible route.