You might find this discussion between the creators of The Silver Searcher and ripgrep useful:

https://news.ycombinator.com/item?id=12567328

RipGrep doesn't have some very useful PCRE features.

https://github.com/BurntSushi/ripgrep#why-shouldnt-i-use-rip...

If you use lookarounds (or often use grep -P), RipGrep may not cover all of your needed use cases.

That said, it's very fast for general use.

I use both ag and rg with fish. For me, both are equally fast (because my repositories are small enough that it doesn't matter), but ag has better UI (I remember the --python option, but have no idea how to filter with rg). Those are about the only differences that matter to me, so I use whatever is muscle memory. Usually rg, unless I want to search for specific filetypes.

If you're wondering whether to switch, don't bother unless you find ag slow.

Fish, on the other hand, I can't live without. I recommend fisherman and z, and a few other plugins I forget now (I use one that shows a notification if your long running command completes while the terminal is in the background, I love it).

I wanted to try fish too, but too many plugins or libs has a warning on github "does not work with fish" so I just saved myself some headaches and decided to resume with using already great zsh.

FZF and fish don't play well if I remember correctly (I hope I'm mistaken though.)