The answer to this question is highly debated. Ask one person and they’ll give you a totally different answer than the next. But, here is my answer based on my studies and observations. A streusel is crisper, a crunchier topping than a crumble. Crumbles are often sweeter and softer. They still have the short texture and crumbly appearance of the streusel, but the texture is different. Streusels often contain oats or chopped nuts, where you do not often find those ingredients included in a crumble topping.