I think manufacture is much more important than material. The genuine CMB plastic QDs are of high quality and I've never had a problem. Knockoffs (especially the Kegland ones) are to be prone to fitting poorly and leaking. Likewise, I and others have found the Kegland stainless ones to be hit or miss. I do have a couple of the stainless ones made by Bobby at Brew Hardware and they are of outstanding quality, design and workmanship -- way overengineered actually, but for just a couple bucks more than Kegland, worth it if you really want stainless. So the upshot is, IME, if you want bling, buy Brew Hardware stainless. But you can get plastic ones that are just as reliable. Just make sure to get genuine OEM parts. And no matter what, watch for deterioration or damage in the internal rubber washer.