Fairbanks received a good size dump of snow almost a week ago, and my trails have just barely enough to switch to a sled. You need a good base of snow in order for the snow hook to take hold and the team can be stopped; especially when there are two road crossings like I have to deal with.
There are 2 great advantages to the sled over the 4-wheel. It's quiet, and the dogs have to work a bit more honestly. So instead of me just throttling along at 9 mph and the dogs either pulling, or coasting; they have to pull to get me up the hill. The dogs also love the sled (I guess that's a third advantage). I think they like the freedom of being able to find a groove a bit more than with the big, heavy 4-wheeler going exactly 9 mph all the time. They like to put on the power sometimes, then back off other times. One of the leaders will perk up her ears and everyone is right there with her; they have more fun with this sort of flexibility.
The disadvantage of the sled is that I can't take a 12 dog team out. I can control the team very easily with the 4 wheeler, thus at the road crossings I'm not worried. 12 dogs on a sled with low snow would be a disaster. So I've broken the 24 dogs into 3 teams of 8. Each team has at least one adult leader and at least one 2 yr-old leader. Then the rest of the dogs are evenly divied up based on age and size. An 8 dog team is still a bear to get out of the yard right now.... I work up a sweat, no matter how cold it is. The trail is very bumpy, narrow and windy and those little buggers are worked up into a frenzy when it's time to take off.
I've included a short video of the dogs running at the 25 mile turn around, just to show the sled and the scenery on a beautiful, crisp (around 20 below 0 deg F) day of training.