Although I think some people can shave with those chopstick razors...I don't personally think they shave anything at all like a traditional straight. That said, they are fantastic razors in their own right. Build quality is infinitely better than any other shavette out there. They blades are all ridiculously sharp. If you can shave with a Feather, you can shave with anything (except maybe a blade glued on some chopsticks....)
I think the difference is the Feather is designed to be a razor. Other shavettes are designed to hold DE blades, which are designed to work in a different device. It's the difference between a device and a jury-rigged device.