What will give DD away is that he is weak.
But he will be the closest to Spider-Man if you don't see his strength.
Cap is almost as acrobatic but much stronger. What can make up for Cap lack of special senses is his perception speed and his cunning ability to predict attacks (Master of aim dodging).
If both engaged a superhuman (in physicality) enemy in a fight then they would quickly discover that DD isn't Spider-Man (strikes are way weaker).
With Cap it wouldn't be as obvious.