>>7005921A food processor typically has flat blades only meant for chopping. A blender has angled blades meant to cause the food to circulate throughout the container, which leads to a smoother/finer result. It also stirs air in which a food processor would not do.
A blender attachment for a food processor makes it a blender, so the comparison between attachments still stands. Try making a milkshake in a food processor and you'll see the differences pretty readily first hand.
