[JFreak]

I do not know of any monitor controller that has either/or switch for speakers and headphones. Everything has mute button for both though. It takes a second to click both, so I have never seen that a problem.

If that is essential to you, there is a solution you can do yourself. First of all you need to route speaker monitoring and headphone monitoring to separate outputs, say 1-2 and 3-4, then have a box that accepts both and only outputs one pair. Toggle the switch, done. Google "passive monitor switching box" and pick your poison. Though most of them also have middle position where both outputs are active. Best ones are expensive because they are really well made, probably even handmade.

Or, if you really want to do it in software, here's a trick. Solo safe everything and then create two distinct monitoring auxes (1-2 and 3-4 outputs) with obviously sharing same input. Then set your soloing to X-OR. That way whichever monitoring aux you are soloing will automatically mute the other one. But it also requires that speakers and headphones have different outputs.