You find what works for you, and you use it. As to the point of the original post, practice what you plan to use. In my opinion, you need to be able to set up you shelter in the dark and in bad weather, with your fingers numb from the cold. The real difficulty for most people is tying the knots and figuring out how to set one up in a variety of situations. Practice, practice, practice. Whatever you use, be able to use it well.

Many new materials allow tarps to be much lighter and to pack smaller. You can find reasonably priced tarps that pack small and provide you a more substantial shelter. I think that a good size tarp will make a better shelter than a poncho, if you have one.

Sil nylon is expensive, but packs small and is light. You can go to a hardware store and get tyvek or other materials and make an improvised tarp for little money. You can get a good sized sheet of plastic and do the same thing. Shelter from the elements is a critical survival skill and if you plan to go out, you need to have something that you know how to use.