Linux is different than other operating systems you might be familiar with. There is no one organization that "owns" linux. Anybody, even individual people, are free to take the linux kernal and make their own version to suit their needs.
I think that's the main source of your confusion: Linux isn't a single operating system, it's many different ones created by many different entities that all just happen to share the same core software at the lowest level.
Since each distribution is made by a different organization for a different purpose, you can't really say which is "better". Each distribution does the job it was designed for very well. For instance, you mentioned Ubuntu (made by the Ubuntu organization). The goal with that one was to make a linux distribution that was extremely user friendly for the novice home user to handle, so that it could be an alternative to people who were tired of MacOS and Windows. So it does the "user friendly" thing very well, and is a great choice if that's what you're looking for, but you may find it deficient if you were hoping for something else.
And there's not any one that's "newest" either. Most distributions release regular updates and newer versions at various intervals, so they're all pretty much equally modern.
A list of different Linux distributions (but remember this list is NOT exhaustive.... there are hundreds of distributions and anybody can make their own at any time, so it's impossible to list them all!)
Ubuntu - Built for extreme user friendliness for novice users
Mint - An offshoot of Ubuntu, user friendliness is still the key goal but it takes a slightly different approach than ubuntu does.
RedHat (Fedora) - Built for people who want to run servers quickly and efficiently
ArchLinux - Built to be as small and basic as technically possible, so that it can fit on tiny, weaker devices. I've even heard ArchLinux being used to power a wristwatch computer!
PHLAK (Professional Hacker's Linux Assault Kit) - Built for network security professionals who want to test out the security on their computers.
PuppyLinux - Built to be a "portable" distribution, meaning it can run off a USB thumb drive without having to actually install anything on the computer itself.
Android - Built to run smartphones/tablets. Many people don't realize that when Google went to make the Android system they actually based it off the Linux kernal.