For the deepest, freshest, driest (fluffiest) snow in Colorado, the northern mountain range is by far my favorite. I ride Routt National Forest's rolling hills, deep and challenging snow, expansive Aspen stands, and tons of near-private roaming room every winter, and whether you have your own sleds or are looking to try something new and exciting, Steamboat has it for sure. There are three activity companies (see local Chamber) if you need a tour guide for just a two hour tour or an all-day adventure with the boys. If you're coming on your own, the forest service office here has beautifully descriptive maps of the trails and meadows, put out by a local "Routt Powder Riders" group of pre-hisoric snowmobilers.
If you've never thought this would appeal to you, don't be judgemental until you try it. I was a tree-hugger in Oregon before I converted to the wild west, and I've grown to love the mobility that snowmobiles offer. There's no way my snowshoes or x-country skis could get me as far back country to some of the most beautiful 360 degree views of the surrounding mountain ranges of northern Colorado - the Zirkels, the Neversummers, the Gore Range, and Hahns Peak, a local dormant volcano. After a hard day (or two!) of riding, make sure you soak in some of the renowned hotsprings of the area. Call the chamber or their central reservation department for more info, these two resources are very well-versed and friendly.