"layup style helmet is made to deform then disapate the shock" ?? ... Deform? -- Most of those things are SO stiff and tough that I can't see that happening, and I would think most wouldn't dissapate the shock as well as a plastic one except for the rare, truly high-speed rock collisions. Maybe the very well-padded ones? Impact-wise, newer plastic ones like the dual-layered and heavily padded WRSI and the carbonfiber-reinforced Sweet Rocker seem like they'd be much better at deforming some and dissapating the smaller-med. hits that make up the majority of contacts. If I were doing serious steep creeking or highwater IV/V, I'd want a FNA X Stream or something super tough, but until then, tougher plastic with good side/ rear coverage makes a lot of sense.
I don't think I've ever come close to hitting my face, and I tuck hard and fast, but sometimes things happen more quickly than you can react to and occasionally hydraulic forces will prevent tucking or even undo it -- that's when faceguards/ chin bars/ etc. are comforting.