Cutting bread into cubes is faster and results in stuffing with a more uniform look. For a rustic result, you can tear some or all of the bread into pieces. Either is fine and just depends on your preference. For this Brioche Stuffing and my Homemade Stovetop Stuffing, I like the look of evenly sliced bread cubes. Many times I will tear some of the bread for my Crock-Pot Stuffing. Check those posts out to see the difference.