Bash and Zsh are both rather great shells to use. However personally I would rather go with the Zsh shell because of the ability to customize. Not only that but provides great functionally if you are using the shell quite often. However if you aren't using the shell than bash will just do fine. However if your like me and use the shell more often then not since I dislike moving my mouse and attempt to soley rely on keyboard than Zsh is the way to go.
A little something that is worth noting about these two shells is that Zsh has significantly more cpu usage than bash. However it isn't anything that is significant unless your running a computer that is dealing with low amounts or ram and memory. Using the time command I found that zsh used around 4% of the cpu to start compared to the 1%. The time for zsh to open was 10 times slower taking 0.12s compared to the 0.01s seconds. While this isn't anything drastically noticable it is something to consider.