I made a Pale Ale in which I made a yeast slurry in a pint of warm (+/- 95 degrees F) water before pitching into the wort. Today I made a Porter in which I pitched dry yeast directly into the cooled wort and stirred it up. Could I have done both beers either way? How does making a yeast slurry differ from throwing the yeast on top of the wort and stirring it in?