I'm in zone 5b and prefer fall planting. Have successfully planted without using an ounce of water. The trees are dormant and need no water. Simply dig a large hole, pulverize the soil and plant mounding the soil. Let the winter and spring rains settle the soil. Then they are in place for that early spring root growth. Who knows it may be too wet for early spring planting and many nurseries ship late, fall planting avoids those problems. Also helps avoid the crack that developes around the edge of the hole that restricts root growth the first year.
One word of caution, if in the North (maybe zone 6 and further north) place 6 inches of mulch over the top to prevent the frost from freezing deep and killing roots. Frost penetrates much deeper in loose soil.
Observation. Someone mentioned winter soil heaving (buldge or lift). I've seen it heave as much as 6 inches here in central Indiana.