Well, the difference all comes down to how one views tmux, and I'm on the side of hating it. I personally use tmux only to background applications, and any of its other features are "bloat" to me.
After reading everyone praising tmux, tmux, tmux, I tried to use it several times, several days or weeks each time. The thing only got in my way all the time, to the point that now I prefer to lose sessions than to use tmux. It has to be a really important and peculiar and heavy operation, to have me still launch tmux punctually.
Not your parent, but here's my take. For remote usage, tmux doesn't provide much beyond vanity over screen, and is less likely to be installed on a shared host. Locally, I generally get by with &, bg, fg, and Ctrl-Z if I absolutely can't open another TTY, and a tiling window manager (or Emacs) provides a superior tiled workflow for the applications I use.
There are some cases where tmux could help me, but my X session and terminal emulators are stable enough where I'm not worried about them crashing and interrupting my shell session. As such, I have no need for tmux, and using it just for terminal emulator scrollback seems hamfisted.
The only use case I can think of is running large distribution updates which might potentially pull the rug out from under your graphical session, but I tend to run those on a non-X terminal if they look sketchy.
Edit: I'd totally consider using tmux as an alternative to X on my Raspberry Pi, but if I have X/Wayland, It doesn't offer me much.