I’ve long been a fan of Bondhus hex keys. They’re stronger than any I’ve used, without being brittle. And their holders, while not as fancy as others like Wiha or even Wera, hold up very well long-term.
The ProHold screw-holding mechanism on the ball end is a spring-loaded ball similar to that found on a ratchet. You can read more about it here. What I like about the ProHold versus Wiha’s MagicRing: it doesn’t scar the finish on the inside of the fastener head, and in my opinion it does not compromise the strength of the ball tip as much as the MagicRing. Of course I haven’t broken the tip of a ProHold or MagicRing hex driver, so this is speculation on my part.
As a bonus, the Bondhus ProHold are made here in the U.S.A., at least for now. I consider that a reasonable reason to buy them over the Wiha if you’re a U.S. resident.