It is only on weaker satellite signals and or really bad weather that a better quality dish will show its superior performance. The differences are in the build quality, reflective properties and the accuracy of beam focus on the LNB feedhorn, if the reflector is not perfectly shaped and the reflective surface uneven, the LNB will not receive the full signal. I'm sure one of our dish experts will be able to enlarge on that though.
PS. Regarding the initial question in the thread, will have to leave that to the dish experts as well .