answer to my question is on the description page of Shpool. Looks compelling.
----
The biggest advantage of this approach is that shpool does not break native scrollback or copy-paste.
I'd say the best part is not needing screen on the server.
If you have several servers and several people that like several multiplexers, you would need to install all of them in each server, and manage configuration etc.
However, you can have your own multiplexer and use shpool on a window to connect to a server.
Done, you have your favorite multiplexer, with your configuration, and the only tool in the server is shpool