Ten will always be my favorite, but Nine is a close second. (I've never connected to Eleven and was quite glad when his run was over.) I like the darkness of Nine because it fit with what had happened to him during the Time War and showed just how alone he was. I think Ten's more "goofy" because when he regenerated he had Rose, someone who was his friend, and he didn't have to carry such a heaviness of being alone. But he still could be dark; which I liked that he kept that part of Nine.