I would completely disregard using Windows for servers. If you're in the business of running webhosting I think you should take the time to learn Linux. It is really not that difficult and the Windows based P's are all severely crippled and/or lacking behind their Linux counterparts both in terms of version, reliability, security, performance and cost.
Which CP you would choose I think depend on you and what you want to do with it.
If you are running your own sites only, or only expect to give users FTP access Plesk looks nice. It has a somewhat easier learning curve for administrators and users alike. This is also the solution that will give you best performance = most sites on a server for any given server load.
If you expect to give your users shell access there are no alternative to Ensim, using High Security mode for sites. It is not without a cost though and you should not expect to be able to host anywhere near the same number of sites in this environment as in Plesk (or Ensim Low Security).
Cpanel - has a large following mainly for historic reasons - they were among the first around and way older than Plesk or Ensim. It always reminds me of a big house that started out as a small house and had a large number of annexes bolted onto it.
Helm thankfully doesn't exist for Linux but I find it quite similar to Plesk in many ways.
My opinion - feel free to disagree