How do NNN bindings mounted on cross-country skis with NIS mounting plates compare with the screwed-in versions in terms of reliability (are they more likely to break) and performance (do I get anything from being a bit higher off the ground)?
Reliability: So far so good - no mass returns of skis due to breakage. Since the binding plate is integrated into the ski, there is more even distribution of force, where as five screws create five weak points.
Advantages: The biggest advantage comes from being able to dial in the "sweet-spot" of the skis. Ski's vary greatly in composition and dimensions, and shifting your bindings forward or backward by centimeters to adjust the center of gravity can make a world of differences in their responsiveness and handling.