A thoughtful question,
with lots of variables,
a heavy bow generally propels the same arrow from a lighter bow faster,
imparting more energy to the arrow;
but this is not always the case however,
a lighter draw bow may have very efficient limbs that are faster than another bow of another design with a heavier draw,
by properly matching the arrow to the bow you may get as much speed from the lighter bow as you do the heavier bow;
however as you begin to shoot a heavier arrow the heavier bow will continue to propel the heavier arrow at a given speed while the lighter bow with fast limbs but with a weaker draw will begin to propel the heavier arrows slower, reducing penetration, range, etc.
Since bows kill mostly by bleeding lighter bows work very well,
until you engage heavier targets, with more tissue and bone to penetrate,
in which case a faster heavier arrow will penetrate much better,
increasing the lethality, and perhaps increasing your range.
Disclaimer: Discussing this topic may cause brain damage