Vote to CentOS.
CentOS,widely used for webhosting and supports prominent control panels available in hosting industry.
Regulars bug fixing, kernel updates and patches available.
Easy to manage and administrate. Trouble shooting is bit easier and community/forum support is good.
When it comes SQL or database hosting then windows hosting is fine for me and but the downside of windows is it can be easily hacked.
With Linux you will get a stable server platform with top-notch security. Resource utilization is much better in Linux. I would prefer using CentOS