Typically a bow with an 8 inch brace height is more forgiving then one with a BH of 5 3/4.
A/A and cam design also come into play as well.
How important is it--------all depends on the shooter and his skills.
If your looking for a hunting bow,speed always isnt the #1 priority.Look for a bow with a brace height of around 7 inches .
Also the lighter the arrows the more finicky it can get.Shoot alluminum arrows or heavier carbons in the 400 grain class and will be more forgiving as well.