Thickness adds more draw weight than width,at about a 3 to 1 ratio, so theoretically a thicker, narrower bow of the same draw weight and some material will shoot a little faster than a wider thinner bow of the same draw weight and material, however a wider bow will give a little more stability, or resistance to limb twist, especially in a highly reflexed or recurved design, that's why most longbows are 1.5 and recurves 1.75. After tillering longbows usually end up around 1.25 and recurves 1.5.