One of the things I like most about tmux is the scrollback buffer, which you can scroll through and search and copy/paste any text in the shell output with vim-like keybindings (you have to configure it for vim-like keybindings, otherwise it's emacs style). It makes my workflow very efficient. I haven't found a terminal emulator with such convenient features and keybindings. And searching, copying and pasting are things that I do a lot in my terminal.