Hierarchies and tags are not an "xor" proposition. I always use both at the same time. Hierarchy gives you a way to organize things according to each others.

Hierarchies and tags are not an "xor" proposition. I always use both at the same time. Hierarchy gives you a way to organize things according to each others. I want hierarchy, because if I deal with thing A, I may have then to specifically have a look to child B or C. It helps with context and granularity. While tags allow you to attach multiple categories to things and filter according to that. You can use a hierarchy as a poor man tag, but really, you should use both.