I'm a convert from the Marathon Winters to the Nokian Extreme. Let me tell you why.
Years ago I decided that I was going to commute by bike as much as possible. Since I live in an area that gets a lot of ice and snow, that meant buying studded tires. I went with the Marathon Winters, looking for something with good balance and being new at the whole thing - I wasn't sure it was going to work out.
The Marathon Winter is a good tire. It's been outstanding on smooth ice and the lack of rolling resistance is impressive. I've never had a flat with them, as far as I can remember, and that's over 2+ winters of commuting. The problem is that it isn't good on snow. Not even relatively shallow snow. Even at minimum pressure.
I didn't even consider the likes of the Nokian Extreme before, thinking they weren't made for roads. And they probably aren't. But guess what? The rolling resistance actually isn't all that bad. Compared to mostly slick tires, I am slowed down by not much more than 10% at most on clear roads. In fact, the difference from the MWs really isn't a big deal at all. And the performance on snow is much, much better. They work better on high pressure than the MWs did on low pressure. On ice, they seem to do just as well. I traversed a heavily-rutted MUP (thanks to icy shoeprints) other other day and it was manageable with nary a twitch. With the MWs, I would have been walking.
Do you still have to be careful? Absolutely. Will you be slower? Just a little bit. But I am convinced that if you want to ride as much as possible and have to deal with accumulating snow, get the Nokian Extremes and be done with it. Don't beat around the bush.