Without parameters, there are a number of ways that the subject can be interpreted.
For instance, what if an untrained Shang-Chi arrived at K'un Lun just around the same time as Danny? In terms of skills, they would be on equal footing, no? And thus Shang-Chi would not be better in the martial arts than Danny. Still, I could see the two having had a rivalry, with Shang motivated to be a perfect weapon for his father and Danny motivated to seek vengeance for his parents. That would make for an interesting story.
What if Shang-Chi were to take over the Iron Fist title? Perhaps in this scenario Danny would have given the title to Shang and then Danny would become the new Yu-Ti in K'un Lun. With Danny out of the way, Shang-Chi with the Iron Fist would be THE premiere martial artist in the Marvel Universe. There would be a huge target on his back and he'd have to contend with challenges from martial artists, tough guys, and psychopaths like Mr. X, Bullseye, Zaran, Batroc, and others. Not to mention that he'd have the responsibilities towards K'un Lun as well as fighting against the evil plots of his father.
The only thing I could say to that is that Shang could have some very, very interesting possibilities with the iron fist indeed
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