Custom dedicated servers allow your business to implement any solution a dedicated server can provide to the fullest degree. You will be able to configure it to meet the exact requirements of your infrastructure’s purpose in all aspects, from the choice of hardware to the choice of OS and other software. Custom servers are also easily scalable, allowing you to upgrade them if needed.
When it comes to custom dedicated server hosting, there are almost no downsides to speak of, as they can be whatever you require them to be. One of the few cons of custom servers is their price: they can get quite expensive. This is offset by the fact that you have free rein to choose components in any price range. As a side note, you may not need to build your own dedicated server if your company's tasks can be solved with a pre-made configuration.