I have halyard locks, but still PREFER the old time wire-rope with multiple swaged balls and ball cleats - bombproof, cant possibly slip, cant be inadvertantly opened .... and simple as hell.
Hell, one boat that I just got rid of had the ball cleat near the mast top on a rotating mast .... no halyard stretch at all as once set into the ball cleat there only remained ~2 feet of wire being under elastic strain ... very precise!!!!!
I dont know of many who would put a halyard lock at near the top of a mast, .... unless you have an aggressive and agreeable bowman.
Calculate all the elastic halyard strain you get even with 'tech' halyards, and see what 'stretch' you get under a full winched-up or sail/wind load. ;-)