I've not compared my Dynamic saddles (carbon vs steel rail) on the same bike but I did compare the Romin Evo Pro (carbon rail and firmer material) vs the Romin Evo Expert (hollow Ti rails with gel padding) on the same bike and found the carbon rail saddle a lot more comfortable overall but that is probably partly that I prefer less padding.
I think it is good to have carbon somewhere in your bike, whether it seatpost, saddle rails or frame as it should reduce certain vibration frequencies. Although I've yet to ride a carbon frame.
I've not compared my Dynamic saddles (carbon vs steel rail) on the same bike but I did compare the Romin Evo Pro (carbon rail and firmer material) vs the Romin Evo Expert (hollow Ti rails with gel padding) on the same bike and found the carbon rail saddle a lot more comfortable overall but that is probably partly that I prefer less padding.
I think it is good to have carbon somewhere in your bike, whether it seatpost, saddle rails or frame as it should reduce certain vibration frequencies. Although I've yet to ride a carbon frame.