I don't know what's wrong with Ten either, and it's frustrating because I really like Tennant when he's having one of his good moments, and yet really despise Ten when he starts with the self-pitying whinging. Seven was a much more mature and serious operator; as you say, ruthless without making a big deal out of it, doing what he thought needed to be done without the unnecessary angsting. I think he probably would have won the Time War had he been participating in it, but that's probably a thought for another time and another fic. :)