Which is better for visa application, Ho Chi Minh City or Hanoi?

No if you enter through HCM you have to apply to the HCM consulate. They want to see the stamp in your passport and a hotel booking so they can see where you entered the country. After applying you could travel to anywhere in the country. I don’t think they ever ask people in for interviews, but they can, in theory, which would require you to come back to the city you applied at.

As for which one is better, dunno, I applied in HCM and am still waiting. They say 5 business days (which is today for me), they didn’t ask for additional information, so hopefully I’ll get it today 🙌🏼