I have ridden at Swinley for many years and my wheels always remain firmly on the ground. I have been to Afan and Glyncorrwg twice and loved them both. There are bits that get the heart racing but by far my biggest shock is always the climbing.
Personally I wouldn’t bother with them, boring, repetitive, once you’ve ridden one, you’ve ridden them all… what’s wrong with getting a map and exploring the vast network of natural trails there are out there?