I covered that earlier in the thread - heavier limbs for the same draw length mean more power and therefore arrow speed and a flatter, shorter trajectory to the target. But the trade off is you need bigger muscle cells (which reduces accuracy) and you will fatigue them quicker. The further you shoot and the rougher the conditions (ie outdoors) the more important it is to have more power, but if the conditions don't need it then all other things being equal the guy using a lighter draw will probably hold the advantage.
Ergo most of us end up using two sets of limbs which we swap between, using the lightest we can get away with for the type of shooting.
If you find the weight fine then that means you can concentrate on technique.