Also, they are offering VPC by default, the nodes seem to have only one network interface which defaults to private network, and external traffic is routed to private network with specific firewall rules. Also, they are offering ip failover, I think you can attach or move external ips at runtime between servers without configuring anything on the nodes (just from API).
For online.net I know they are offering DDOS protection for higher priced servers, I'm now sure if they are supporting this for scaleway, but you can always reverse proxy from online.net server to scaleway to achieve horizontal scalability if this is an issue.