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

Your MVP or solution will definitely change so having an audience that is interested in the problem you are solving is more important.

For me, MVP.

vote for building an MVP since I follow the PLG

I'd build the MVP - my audience needs to see what I am building for them to see the value. Also, I want to attract a niche audience who will have the higher probability of converting as early paying customers.

Honestly, I don't think you can choose just one. We are building our product and balanced too much onto development/product part, without focusing on the audience enough, and now we have to "catch up" on that to move on. If you focus on bulding your MVP only, you may end up at dead end where the cost of further development is simply too high, because you didn't verify your choices enough. If you build an audience without the product, you may find it difficult to keep them interested before your product is ready. So I'd say - build stuff and keep everyone notified about that ;)

For me MVP, if your product can potentially solve an existing problem then the audience would naturally come. It's not like you don't have to build an audience, you still have to but if I can only pick one then MVP

I think it is important to do both simultaneously. However, I'd spent the majority of my effort on building the MVP so that the functionalities and features are ready for the users when going live. The audience can grow through personal networks at first. Only when the product is live, I'd get involved with heavy marketing efforts (e.g. SEO)

Both are required actually! If you have an MVP then you need a target audience in order to test the MVP. We can't test the MVP with the internal team, right?

Both building an audience and building an MVP (Minimum Viable Product) are important. However, the priority given to one or the other can vary depending on the specific circumstances of the startup. If you have a unique and innovative product idea that solves a real problem, then it is important to have a working MVP to validate your concept and attract potential customers. Building an MVP in this case would be the priority. On the other hand, if you are entering a crowded market and need to differentiate yourself, building an audience first through marketing and branding efforts can help establish your brand and create early demand for your product. In this case, building an audience would take priority over 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.