Bulldog are you saying by dirt IF you mean the skinned ones like softball uses? If so then I say NEVER to those. I had to play on one in high school back in the early 90's and we worked like dogs on it if it rained.
I think it's harder to keep a smooth crown on it because of erosion and if you do the whole ditch to drain puddles it just messes up the field.
Grass all the way. I love the look of a great field with dirt basepaths but it's a lot easier to maintain if you make those grass as well. I can't go with you j2 on the whole grass IF except for the circles around the bags, mound and plate. Looks too much like astroturf to me. I bet it would be easier to maintain though.