Splicing is easy, durable, and dependable. It is unusual for a splice to bind on a sheave in the mast.
The SplicingNut is an clever invention, however I'd be inclined to first experiment with it at a location where you can monitor its longevity and performance. Someplace where if it fails you can quickly tie a knot to replace it: perhaps the mainsheet or traveler, not necessarily the top of the mast.
Read both the Disclaimer and Warnings, they are quite stringent: in part "The working load is a guideline for the use of a SplicingNut in good condition for non-critical applications and should be reduced where life, limb, or valuable property is involved, or exceptional service such as shock, sustained loading, severe vibration, etc."