Plastic buckles and D-rings. Delrin's tough but having broken them and then have the straps wrap around the wheel (which broke the straps and was a bitch to get out), I don't use plastic no more. On the boat I only use plastic, but them I'm not concerned with a bag falling off un-noticed on the highway. But if you just want pretty, it's pretty.
loop around the frame straps can do little else. not so good. ideally evry piece of gear can do a number of things. I use a simple loop on the frame rails and take my straps/bungies/whatever off those. A small loop or grommet in the end off a strap is used to restrain the end with a bungie. "tucking it in" doesn't work and can be dangerous depending on the length of the tail.
These people might advertise in MOA-N and Airheads (simple by birth) and they can certainly copy what everyone else is doing, but to they do any serious touring? Decent price tho' @16.50 for a pair of straps.