Unlike a crimped connector, a wire nut requires no special tool and can be reapplied.  I think the most important feature is a live spring - one with room to expand around a bundle of conductors.  This can make a more secure connection and accommodate a larger range of bundle sizes.  Two other good features of the GB 10-086 are the long skirt (to prevent shorts) and the square cross section of the spring wire (to hold the conductors more securely).