Positive laws are laws made by humans. They were established through practice and have stood the test of time. That is the main reason why positive law theories believe in the "law's capacity to advance the common good etc." To them it seems to have worked so far.
Natural laws have to do with the inherent human rights such as the right to life. They are not to be trespassed. Theories of that kind support law as one "ensuring social order and welfare", but they are displeased with the way it can provoke immoral behaviour and be used for evil purposes. They propose that the legislators should take more time to revise the law's content and develop institutions, which are to follow its administration.
I am not very well aware of the legislative process, so I can't really discuss newly enacted laws. However, I agree with natural law theories that there are not enough institutions who follow the actual administration of the laws, in our country especially, because I know for a fact that in Germany most people are aware of the laws and they themselves take care to abide by them. Unawareness is a huge problem, because it can lead to disregard of the laws, both natural and positive.