I don't know about the OP, but for me the reason is that it's made by a company with a much bigger profile than yubico

This means that it's under much higher scrutiny by the public. Due to that big profile I also expect security issues to be fixed quickly as Apple has much more reputation (and money) to lose than Yubico.

Finding exploits in the iPhone's secure element gains you much more fame than finding exploits in the Yubikey.

And finally, Apple has come out very publicly against aiding law enforcement and has a much bigger war chest to fight requests by law enforcement.

Yubico has neither.