Suse, Fedora and Mandriva are all distrobutions of linux. Each has the same ( more or less ) operating system. Kernal versions vary for each.
What is different are the tools for each. That includes things like a package manager for installing software, tools for configuration etc.
Each distributes various versions of common software. Each has its own philosophy on when to put in a newer release, and how to test each.
As a user this gives you lots of choice. Try one, if you don't like it, try another. This is different than windbloze, you get one system, like it or lump it. You get to pay for all your software, of course you don't illegally copy it, do you.
Is one better than the other? That is up to you. I have tried several, and I settled on Mandriva. I also like Ubuntu. I lke the choice. The more I learn, the more likley I'll move to Slackware some day soon. My