Adam-based life has the tree of life, and is like a god. They are immortal, capable of changing to survive any condition given time, and have indefinite power. They are almost perfect. What they lack, though is knowledge. They are not aware. They cannot comprehend. They simply act on the fundamental instinct that drives them. They do not reproduce because they have no need, being immortal, and no desire, being incapable of comprehending the notion.
Man is weak, frail, and inevitably mortal. When we struggle, we die. Where we fight, we lose. We know death and we know fear, and thus, we breed, trying to spare our species the fate to which we cannot be resigned, and thus dooming ever new generations to the same. And yet, knowledge is our strength. Where we are weak, we can make ourselves strong. We cannot fight, but we can create what can. We cannot win, but we create our own victory. What pressures us we overcome, the fear of death driving us harder than any instinct could. We are dying, and thus, we thrive.
That is why Kaworu regretted the necessity of ending mankind. Though it would be a mercy to end us and spare us an eternity of death, it would be the end of an infinity of creation. Should Adam win, his creations, fine though they are, will be indefinite. Lilith's creations are themselves creators, and thus her works are infinite.