I've played both games, but I personally prefer PUBG. Not because it is more polished or anything, which it's not. I prefer it because of its quirks, glitches, bugs, and other problems. The game is already an edge of your seat game emotionally, but the glitches and bugs add an extra layer of anxiety of not knowing when a problem is going to occur. I'm sure that doesn't make sense to a lot of gamers and frustrates a good amount of people, but I play the game for the experience, not necessarily for the win. My favorite is having a member of your team get booted in the middle of a fight, or having worse when they are driving a vehicle. The panic that ensues is great entertainment. These guys have some great videos spoofing the problems with the game. The language is a little NSFW.
I'm in the same boat, I've played both but prefer pubg. If there were a mode in fortnite that didn't have the building aspect and having to survive with your surroundings as is. I would probably get into it more. I love Viva La Dirt league, they have another series called Epic NPC man.