Sway bar helps keep the sled level.
Think of it as a link between the skis that attempts to cancel roll in the body of the sled.
It does this by transfering force from one ski to the other, so that if you corner hard right and the sled tries to roll towards the outside ski, then the sway bar will be pushed up on the left, and will try to lift the right hand ski correspondingly, which will in turn try to cancel the roll of the sled.
In my opinion sway bars work well right up to the point that the inside ski is lifted, at which point if you arne't leaning you are screwed.
If you do alot of riding on the seat on trails perhaps you'll like it. I have one in both our family's touring sleds. But took them out in any of the sportier sleds i've had. Reason being that they help cornering the big heavy 2 up sleds. But I take care of it by standing my weight on the inside runner of the ski and leaning out when riding solo.
if that makes sense.
I feel like I cannot lean as hard with a sway bar, as in if its there I have to work more to get the sled to roll into the turn enough to corner really aggressively, which never is an issue riding two up on trails.
