I'd put Hetzner in the same bucket as OVH: solid infra company at a more than competitive price, but lacking in managed products. In my experience, they're more reliable than OVH though.

Outscale has the advantage of a huge pile of money behind them, as well as a natural endorsement from gov agencies. They'll lack the niceties, but provide certifications from day one. Different motivations. They're not really meant to be a public cloud in the same sense as the big three. It's kind of the same deal as the Lidl "cloud", which is more of a private cloud managed by someone else meant to run SAP monsters.