What's more valuable in the very early days: building an audience or building an MVP?

In most cases just having a good product at the start is not enough. You need to have strong distribution too. This could be having an audience or bringing lots of organic traffic via SEO. Ultimately you need both good product and strong distribution, but at the early stage I feel distributions matters more.

I think both are important and none of them could work out well without the other! You need an audience to get feedback as soon as possible, but you also need an MVP to be prepared if your audience says your product idea is not valid. A good idea is to build an audience for your personal brand and later on when you have a new MVP you can use the same audience to get feedback from.

How do you have a valid MVP with an audience?

If I had to choose one to focus on FIRST: building an audience. It's difficult to test your MVP and gather proper insights without an audience.

Both

MVP for sure.

Audience/target customers. Without them what's the point of building something?