Dartwick, one of the keys to an efficient bow is getting the early string weight to rise quickly. With two bows of equal poundage the bow with the most early draw weight will store more energy and, everything else being equal (mass, length, etc) will be a faster bow.
Recurves accomplish this b/c in the first few inches of draw the bow behaves as if it were a shorter bow - the string is making contact with the limbs... the more contact the "shorter" the bow and the quicker the draw weight rises. r/d lonbows really have to play with limb taper and where in the limb the deflex reverses into the reflex - you need to tips to act first as levers to get the nice fat force/draw curves.
In either case after the limbs uncurl or come around the bow starts behaving as a longer bow and draw weight rises steadily until the stack point - which is where the string angle at the tips approaches 90 degrees.