I world suggest you to use CentOS 7, because every big companies or big websites is using this OS.
If you say why CentOS 7, then this is the OS with mostly highly security.
This OS is so much secured that you yourself will also not be able to do anything harmful inside it.
This has got lots of security facilities that the hackers those who were trying to hack your website may loss his interest to hack your website.
So, I suggest you to use CentOS 7.
But before using that you should be little bit expert in using Linux Terminal.
Because without knowing how to edit the security of CentOS you may find it a problem.
It also happened with me when I first started using it.
But you should not get worry because it is same as other Linux, just have little bit tied security.