I can't say any gamemode is the worst or the best, but I personally prefer BedWars the most because it gets frequent updates, is simple, anyone can play it and learn to play it quickly and it's much less luck-based compared to the other minigame, SkyWars. BedWars can also be played with up to 4 friends which is a huge plus in my opinion, although almost all game modes can be played with multiple people.
My least favourite game mode is most likely Survival. It's well-made and is overall a good mode, but I just never had fun on it because it's mostly about... surviving. That doesn't interest me much in any way, but it's a good mode nonetheless. It's just not my type of thing.