1) tend to be more consistent as to light output;
2) tend to have more frosting and more even frosting;
3) tend to be more consistent about having their filaments near centre; and
4) don't have writing in the wrong location .
Many enlargers require bulbs designed for particular voltages, particular wattages (??) and particular bases.
That being said, some enlargers do work with some ordinary bulbs, but you shouldn't count on it.