I'm a creator and I do not know which of the two games I'm subscribing to?
So PUBG is not that well known now which is why I would do both.
Why?:
As I said, PUBG is not that well known, and when people see your video from Fortnite or PUBG there are already coming! But you have to remember that Fortnite is not so hyped is why PUBG rather bring the clicks + subscriptions (Should).
But if that does not help then take other games.
greet with beautiful!
And sorry about my bad german.
Play what you like the most because your audience's appetite for the game affects your quality.
But if you both like to play then I would recommend you to start with Fortnite, because it is currently in the hype (which also means that you could get only a few viewers because many Youtuber Fortnite just play.
But if you play PUGB, probably less young viewers will look at you because of their age.
For example, I do not watch PUGB because I do not play it myself.
The game is not crucial, you also need to upload regularly, your videos must be of good quality and you have to convince with your style.
Only gambling brings nothing and do not hope, it will take months until you have 100 subscribers.