Correct. I have a book that focuses on the shells that matter: bash and two others. bash is all I need. I am getting to know zsh as of this writing, but that is a matter of preference. Others use csh, but I don't need to.(If I remember correctly C programmers find that one easier for them).
Maybe if you frame your question you can make a proper choice. But don't let your choice be driven by popularity or ratings. All these shells have been around except for dash, but if you go with dash simply because it's the flavor of the month, will it work for you down the road, a few years from now? What if somebody handed you his laptop with linux on it, but he cared not for dash; can you list his directory contents or cough up a menu? We're not here to dictate, mind you. Ultimately you will work on your PC. How often will you run into a command line? Will you just shrug and say, no dash--no deal. But bash will be there so I will know my way around. Later on you may have benefited from learning dash because it helped you get more out of your system, or you met someone at a user group LAN party or installfest who is learning it too. But these are fictional what-ifs. Like when someone tells you that Jason Bourne used bash; don't believe a word of it
In case you have a hard time choosing a shirt, pick the black one with the words "Bodhi Linux" on it.