Why 4th Edition Champions?
If you're going to run Champions why not the current edition? If not the current edition why 4th? That's two editions ago.
I'm not entirely sure I can answer the question reasonably. It's largely a personal preference. I do think 4th was the last edition the had that special balance between single, honking huge rulebook and still within reason. 5th's book was a hernia causing monster and 6th...so badly marketed in my opinion. Three books or is it two? And Champions, the Superhero parts of the Hero System, are in another book? Way too expensive and confusing.
Plus, fourth edition had a cover by George Perez. I know I mentioned that in a previous post but seriously now...GEORGE PEREZ. As much as I love M&M it does not have a George Perez cover (though DC Adventures has Alex Ross. Touche' Green Ronin. Well played).