I have four sets of studded Schwalbe tires and two sets of the Conti "studless" winter tires for three bikes I tend to ride in the winter. When things are really icy, my 29 x 2" studs on my longtail utility bike are by far the most stable choice (that bike with studs is a tank in the snow).
With patchy ice and bare pavement, my favourite combo has been a studded tire up front for solid cornering and a studless tire in the rear to reduce rolling resistance. It is less likely that your rear tire will slip out from underneath you, especially with the extra weight over it, but if it does, it is a lot easier to recover than if you lose a front tire. So I think it is a great compromise. Been riding that way the last three winters here in Calgary, and it has worked out great.
By the way, it is pretty easy to replace studs in the Marathons -- I have lost a few, but found a nifty tool to replace the studs (unfortunately, it has no brand name on it) but I think Nokian makes one too.