Has there a preference emerged amongst people running a node/bakers for a type of Linux system? I am currently running Ubuntu 18.04. My friend is running Fedora. Is there any advantage in using either of the two? What are people using? Any preference? If yes, why?
As mentioned any answers will be subjective and it really doesn't matter which Linux you choose.
I would suggest either using the Tezos docker image for this and then it really doesn't matter, or look at the linux distro the team choose for their Dockerfile and use that as your base distro. You certainly couldn't go wrong there.