I've wondered the same thing. Some of the lower cost vendors sell the unit, but not the whip. I suspect for all the lower cost units, the whips will interchange.
I do know from this thread that some vendors are not making the whips correctly.
i didn't think getting an answer on this would be hard but maybe its seems risky and not safe to try another brands whip or a cheaper whip. ill probably just go with the Genus to play it safe.
let me know Paul F if you find out otherwise or ill probably order the Genus in a week or so.
There is a standard size for the socket and the whips are supposed to fit that standard. Whether the cheap ones will actually fit and how well is another question, but they're supposed to.