Proton has cooperated with subpoenas on multiple occasions leading to the user’s arrest.

While they may challenge them, the point is that they have cooperated and thus are not reliable. There are no reported cases of Mullvad doing the same.

There are ample links from multiple sources that describe this with a simple search.

Mullvad hasn’t yet shown themselves fed- friendly.

Proton has.

Mullvad is the answer.