回複：why is it better?

Because technically, based on a DOS / BCIS(now USCIS) official rule, those who apply for a visa in Canada/Mexico are not eligible for I-94-only re-entry.
Your having the new I-94 (and you should make a copy and save it as your record) is just a good record keeping showing that you obey the rules and did not sneak back to US based on the border officer's remiss. You have another entry left that you can use it when returning from China to US.