From my experience screen isn't on a lot of systems either. Usually the admins that I work with are willing to install both/either at request.

screen has the equivalent to sessions as well `screen -ls` will show them whereas `tmux list-sessions` will show the tmux ones. A window is composed of panes (analogy from physical windows, pane of glass). An instance is one user on a session.

Very much depending on what sort of installation (not the distro itself) you've got. Most of Minimal installation doesn't come with screen nor tmux by default.

> From my experience screen isn't on a lot of systems either.

Can you name one distro that doesn't include it by default? In my experience you can rely on just about every system having a core set of utilities: bash, vim, screen, ssh etc.

I'd cross both vim and screen off that list. I know Debian doesn't come with vim installed by default, and uses nano as it's editor. Sure it's trivial to install, and many admins install it the first thing they do, but it's not there by default.

vi is present in Debian by default (though not the default $EDITOR)

Debian Wheezy (and all Debians I've ever worked on prior). Not installed with a bare-bones server install.

I swear I've had to install it before on Ubuntu. This would have been awhile ago though.

It's not on Ubuntu, and IIRC not on CentOS.

I agree with you that if you have to work with multiple systems where you do not have control over installing packages, you might be better off to use pre-installed screen and vi with default configs so you can get right to work.

But if you have your own workstation and do most of the work with this workstation, tmux + customized configs might be a viable option. It just depends how good your muscle memory will keep up. :)