I use fish. I really like that it is already configured to be a comfortable and usable interactive shell out of the box.
The differences from posix are generally easier to remember on the fish side imo (like if statements) and you generally only encounter them when you write scripts.
You can also write scripts in bash if you want and there is a nice tool if you need to put environment variables into shell from a bash script (https://github.com/edc/bass)