The difference is that the extract is "standardized" for something(I put that in quotations because without knowing what it is standardized for, it doesn't really mean anything), and the root is literally just 150mg of the plant root dried and ground down and thrown into a pill(completely useless IMO).
When using nettle root, I'd suggest looking for something that is standardized specifically for 3,4-Divanillyltetrahydrofuran. Testabolan by iForce is a great option, and user reviews on it are absolutely stellar. In addition to the full dose of the 3,4 you also get a full daily dose of ALCAR, which is one of my favorite ingredients.