I can't speak from experience with those exact models, but I'll say that contemporary mobo audio in general is far better than it has any right to be.
Seconded. Aside from the wimpy output drive, and the fact that Realtek's reference designs tend to spec too low a value for the DC blocking caps to drive headphones (-3dB at 50 Hz into 32 ohms), I'm amazed that most current mobos from top-tier vendors manage to get the level of audio quality we're seeing these days. A motherboard is a pretty horrific environment in which to be doing high-quality analog signal handling -- power spikes/dips and and EMI galore.
Feed it through a headphone amp (or powered speakers), and onboard should be good enough for 99%+ of use cases these days.
The presence of those components would make think that onboard audio is just as good if not better than the Creative stuff.
Well, based on some (admittedly cursory) research, it appears that the OPA1622 is a $3 part in quantity. Given the highly cost-sensitive nature of the motherboard market, I don't think they would've used it if they didn't think it gave them a competitive advantage, when many other "good enough" op amps are available for significantly less.
No idea what Creative's "custom" solution looks like.
So who knows...
Plus, there's the bonus of not having to deal with Creative s***t drivers.
Yes, there's that!