I like KDevelop. It is a great product. Especially after (v5.0 I think) they integrated libclang to their auto completion. But I would say QtCreate is more polished and more robust version of the (idea of) KDevelop. They both trying to achieve the same goal. They both wan to be C++ IDE (although QtCreator does support Qt Project in a special way). But in broader sense they both want to be general C++ IDE for C++ developer.
I prefer QtCreator, just because it is more polished.
I prefer QtCreator, just because it is more polished.