Neither! Do yourself a favor and get a real cock ring.
For something with a little bit of stretch and I really do mean little bit, try one of the Tantus cock rings like the C-ring intermediate or for a Vibrating C-ring again a Tantus product. Or I'd recommend a metal one but remember you must measure and get the size right. If you've only used one of those worthless real stretchy ones you have a surprise waiting for you, a good surprise... enjoy!