Both are good games, but I prefer PUBG over Fortnite. Fortnite is fun, but I do not really enjoy the building aspect of it. I like PUBG's realistic approach. Fortnite runs a lot better though than PUBG, but that's because it is a finished game. Just keep in mind that PUBG is a work in progress so you will encounter glitches and have low performance.
As for which console, I would get it for Xbox One. It doesn't run as well however on Xbox One, you have a level playing field. Everyone has the same specs. You don't need to worry about others who have smoother gameplay than you. I think the biggest thing is that everyone has the same graphic settings. On PC, PUBG players will lower grass density and stuff to get an advantage but that cannot happen on Xbox One. It's the same throughout.