For me the killer feature is truecolor support. 256 color is rather limiting, and with truecolor you can also use gui syntax highlighting color schemes. My actual shell runs in a neovim :term, with neovim running in alacritty, so I dont care about fancy terminal features other than rendering and colors.
I used to use tmux but the vim commands were incomplete, and even with vim integration plugins, the separate buffers and separate window splitting gets in the way. I wanted to just use the same pane splitting and navigate and use the terminal output the same way I use my text in vim. Neovims term was good for the purpose, supported all the term stuff I needed, and I could open straight into it unlike in vim, so I switched to neovim. I've had no issues with terminal
stuff since so I've no desire to switch. I also prefer the scrollback history in nvim over built in terminal emulator scrollbacks that I've used.