This looks a lot like an essay, which isn't really what is about, but I'll give some general points to help you do this yourself:
Cornucopians believe that human advancement will outpace the scarcity of resources, so that no intentional efforts need to be made at population control. In the 21st century, the idea has become that human technology is advancing so rapidly that it will easily outpace any challenges that put pressure on human population growth.
Neo-Malthusians believe that an intentional effort needs to be made to limit human population growth, and eventually even to achieve negative population growth, since there is necessarily a limited amount of resources on the planet which will eventually put a painful check on exponential human population growth through disease, war, starvation etc.
There is validity to both ideas, but I generally agree with Neo-Malthusians. One reason is that techonological advancements are not evenly distributed, and the parts of the world with high population growth today tend to also have lower development and less access to technology that Cornucopians argue will keep them from experiencing a painful check, as described by Neo-Malthusians. In other words, the Cornucopian argument may apply to more developed countries, whose population growth is naturally slowing or reversing anyways, but not to the areas of the world where population is actually still growing exponentially.
Another factor is the fact that, even if technology can prevent the painful effects of overpopulation that humanity has experienced in the past, it is difficult to imagine a world in which the planet, and humanity, are better off with more people rather than less. Even if humanity can survive exponential population growth on earth, quality of life will be higher with fewer people.
A third reason is that the timeline for more modern Cornucopian arguments, such as the idea that humans can eventually expand to other planets and thus have virtually limitless resources, is vague and it is impossible to tell whether we will achieve this in 100 or 1,000 years. There are enormous obstacles to achieve interplanetary status, such as the vast distance we'll need to traverse and the inhospitable nature of all nearby planets.
