I watched the whole debate. I am not American and thus will not be voting. Truly ? I don't care so much who wins, only what happens afterwards. In my own view, there is no way that much power should be in the hands of any one person. I am British and we have a monarchy so I am not being a critic.
At the start Clinton seemed very nervous, she gave a lot of detail about her ideas/plans, for me ? Overload. Trump was much more assured, but very lacking in details of the promises he made. As the debate went on, Trump raised his hands a lot, and pointed and waved his finger. In body language this is symbolic for a club. High hands are a typically aggressive sign. He interrupted Clinton numerous times.
As it went on, off question he winced, grimaced and scowled, very often squinting, and looking down - my reading was that he was annoyed to be questioned or challenged by a woman. When he moved onto the 'Stamina' part this seemed much more obvious.
Clinton rallied after a shaky start, in all fairness I think she has been ill. She is a 68 year old who is recovering from pneumonia. Gender is not the issue, it could happen to anyone. Her hands were relaxed in front of her, then as it moved on? Open palms, hands at mid length, palms showing up. It shows there is 'nothing in your hands' it all looked natural, very difficult to manage or fake, probably subconscious. She did say she had prepared, but the body language looked unscripted. She smiled too much at times, trying too hard to be 'warm'.
Trump appeared quite unprepared and unscripted, which maybe explained some of the answers he gave, like "smart" about not paying taxes. As it went on he seemed less confident and angry, the hand gestures increased. Clinton appeared to grow in confidence, her remarks and smile seemed more natural and relaxed, less grimace more real smile. The longer it went on, the more it seemed to go Clinton's way. She relaxed, ignored the taunts, and came back with some humor (not her strong point). Trump is used to winning and looked uncomfortable, head down more often, less high hand gestures, slight air of defeat.
Perhaps it doesn't matter, but purely based on performance, I'd say Clinton did enough to claim the win. Trump never seemed to get into his full stride even after a good beginning.