For me it was that tmux worked out of the box the way I spent many hours getting screen to work the way I wanted. And then from there, just in general the docs

For me it was that tmux worked out of the box the way I spent many hours getting screen to work the way I wanted. And then from there, just in general the docs were better, it was updated more often, and in general was a bit less obscure in how it was configured.