My personal experience cuts it more along the lines of what the other materials in the shoe are. My main hiking shoes are leather Meindl Islands (on my second p

My personal experience cuts it more along the lines of what the other materials in the shoe are. My main hiking shoes are leather Meindl Islands (on my second pair now since something like a decade - the first would probably have worked if it wasn't for an unfortunate accident). They have a decent leather upper and if You keep maintaining it, the leather alone is probably doing most of the job. On the other hand, I think I went through by now about 3-4 pairs of various running/hiking lighter plastic shoes (Merrell, Reichle, Salomon) and in those the membrane is the only thing keeping the water out. Unfortunately, it's generally sewn deep into some plastic mesh, so no way to tell / maintain it even if You'd like to. And one tear in the membrane means that all the water that seeps into the surrounding mesh "will" always find the way into the failed part of the membrane. Unfortunately, the rest of the membrane then tends to still do its part in slowing the moisture on its way out. So it drains / dries much slower than shoes with no membrane.