i need to create a new droplet to serve multiple joomla sites
Which the best solution for performance and security?
Variables are:
Ubuntu 14/15.x, Centos 7.x
Mysql, MariaDB
Apache, Nginx
Php 5.x
You may use any OS since your requirement is not bond to any specific choice of OS.
Points you should keep in mind. In server, usually once setup, people doesn't touch or upgrade as rapidly as your home PC Windows system would do but that server OS needs to be supported for long time, may be 5 or more years for update in security or feature list.
If you chose Ubuntu, install any LTS tagged OS, (LTS => Long Term Support)
In case of CentOS or Ubuntu, choose only x32 if you RAM is less than 2GB.. Opt for x64 only if you have 2GB or more RAM..