Does amount of sperm affect fitness of baby?
I can see where you're coming from, and keep in mind I am no expert in the area, but have you considered that there may be many, perhaps important factors at play than if the sperm had many competition or few? Take the parents genetic and epigenetic profile for instance, meaning not only what the mother and father could each pass on, but whether or not what they pass on will be active or not. And to use your own example, the fittest sperm, who outperformed the larger group; say it required more energy and thus produced more ROS, with which to damage to it's DNA, than the winner in the smaller group - which would be weaker and which stronger? Say the health of the sperm which fertilises the egg could not be influenced by you in any practical way, which method would you choose then?