There are regulations about having spark arrest screens in place and it is commonly felt to be a good idea to have the screens to prevent dirt and insects getting into muffler and possibly the cylinder. That is some possible negatives.
Quantity. One hole plus one hole of the same size doubles the surface area. One hole doubled in size quadruples the surface area. It would take a lot of small holes to equal either method.
Plus, of course, what Crofter said.