One advantage of screen over tmux I found is that it has much better mouse support.
Be careful! New screen tonight.Ubuntu 14.04 server is running tmux.
I ssh into that server from an osx laptop and attach to the tmux session. After a ton of configuration mouse actions mostly work (copy/paste is always wonky).
I also ssh into that server from an Ubuntu laptop. The same configuration I needed to get mouse working for osx is no longer applicable.
I've never even thought of writing a screenrc and it's always worked great.