[mmmmmbop]

It's not difficult to customize. IMO, it's actually easier to customize yourself than bash/zsh because I find the fish syntax much more natural than bash, but YMMV.

That said, I believe that zsh has a bigger community, and therefore most likely a richer ecosystem with more plugins. For example, oh-my-zsh has 142k stars, and oh-my-fish has 8k stars.

However, even with the rich ecosystem of plugins, I wasn't able to get my zsh to be as pleasant to use as my fish, where I only have some self-made customizations (not even using oh-my-fish).

But if having lots of plugins to choose from is important to you, zsh may be a better choice.