A server runs 24 hours a day, often performing complex tasks, so picking a distribution you can trust is key.
Ubuntu is one of the more popular options due to its sheer ubiquity, but it's far from the only option. CentOS is another great option thanks to its reputation for being solid and stable as can be.
Ubuntu is the best choice for most people, but there are some cases where you'll want to consider CentOS.
What Is CentOS?
If you've ever even just read about Linux, you probably know a little about Ubuntu. It's an easy to use distribution based on Debian and it's one of the more widely used versions of Linux out there.
CentOS, on the other hand, may be more of a mystery. This distribution is based on Red Hat Enterprise Linux, which is a paid product. CentOS is freely available and open source but makes use of the work that goes into Red Hat Enterprise Linux.