Having the partial search bound to the up/down arrows is the most fundamental part of the shell for me. I very rarely have to resort to Ctrl-R. Every few weeks I might need a more complex history search, but for that I can just grep in my .zsh_history.

The problem with grep for me is that it's not really interactive. fzf allows me to fuzzy search and adjust the search term and seeing a list with results I then can select from.