Generally, the DIN and the materials are what changes, so that the bindings don't come off, and also so that they can handle the stress generally put on by skiers who need a higher DIN, so that they don't explode. Other things change too, like forward pressure. Most of rossi's bindings have normal forward pressure, but then the higher end axials like the free 150's and 200's have like 30% more forward pressure I believe. This contributes to retention, but is more so that the boot doesn't move in the binding, so that the binding/boot interface is more efficient. If you're coming out of a high end binding alot, have them checked out. The whole reason for high end bindings is better retention with as little pre-release as possible. A shop tech who takes a look at them in person will be able to diagnose the problem better than ns.