I would recommend a primarily tmux-based workflow unless you use a number of graphical programs that benefit greatly from the tiling paradigm.

I used to use Xmonad with tmux (and still do sometimes). I primarily use Unity with tmux now. I came to the realization that tmux had nearly nullified my need for a tiling window manager after I switched from gVim to terminal vim and noticing how much easier it made my workflow. My "ah ha" moment was the discovery of the distinction between sessions, windows, and panes and how each could interact with (or sometimes transform into) the each other.

I'm a xmonad user and I use tmux. I agree that they both provide similar benefits, but the killer benefit for tmux is the persistence. I can have n sessions open and it's still easy to switch between them. Just disconnect the old one and attach to the new one. With xmonad you would either need to have many topic spaces (and recompile config when you want new one) or close the old ones