Neither is “better”. The only similarity is that they’re both battle royale. It all depends on what you want or expect from the game.
Fortnite is more arcadey and the rounds are a lot shorter. There’s far less depth to the shooting mechanics and items in general. Plunkbat rounds last a bit longer and there’s a lot more depth in the shooting mechanics, you need to master bullet drop for each gun and caliber of ammunition. Plunkbat has significantly larger maps than Fortnite and a lot of rounds are heavily dependent on the use of vehicles. Vehicles are completely absent from Fortnite. Fortnite feels much more refined, where you can see some glaring flaws in Plunkbat.
If you want something that’s less complex and easier to jump in and out of a match, go with Fortnite. If you want something more complex and tactical with rounds that are just a tad longer, go with Plunkbat. Or do what I do and alternate between playing both.
I honestly prefer Plunkbat, despite its flaws. The gameplay is more satisfying to me. Winning a round feels like an accomplishment in Plunkbat, whereas it doesn’t really feel like anything special in Fortnite. I’d also like to point out that Plunkbat is running incredibly after this last update. Actually picking up items on first click, no delay, input lag seems to be eliminated, and latency and desync seems to be a non-issue now.