The downside is that they tend to be less reliable in terms of obeying the specs and break unexpectedly.

I've been doing reviews of different dev boards on my channel and have had to send multiple cheap Chinese boards back because they were broken out of the box and a few others were dead within a few weeks of testing them.

For contrast, I have other chips that have lasted for years without issue... And their performance matches the spec (because they aren't cheap knock-off components).

You get what you pay for and with the cheapo ones you're usually trading paying a bit more once for paying a bit less multiple times.