Two-foot tighter turning radius, I didn't believe this back then and I still don't believe it today! Soft snow and water are similar in that steering is done by the rider shifting his or her weight over the track. The skis are usually pointed straight ahead or in the opposite direction of the turn depending how much leverage the rider can generate. There is no way the steel Shaper Bars turn the same as the taller aluminum Shaper bars in soft snow. There is just under a 5/32" difference in the heights and the pocket is larger and significantly further from the ski keel.
Also, Snow-Cross courses use banked corners to help the sleds change direction. Next time you are at a race check to see how many racers use Shaper Bars!
The reduced darting is because they dig deeper, blasting themselves deeper than the existing ruts. The downside is that the ruts they leave will catch other Shaper bars in time, as well as other lower profile bars. Every season I have Shaper bar owners calling me for Ski Savers to make their riding more enjoyable!
USI has a history of making aggressive skis that increase the effort to turn the handlebars. Both their Project-X and SPX skis were notorius for exhausting snowmobilers which lead them to make their Triple Threat skis.