I would say transparency/security, quality of the client(s) and customer service, in that order. It's one thing to offer a VPN service, but to make sure you hav

I would say transparency/security, quality of the client(s) and customer service, in that order. It's one thing to offer a VPN service, but to make sure you have a nice app on both iOS, Android, MacOS, Windows and Linux seems like quite an investment.