You're not wrong. However, Trump is a man without shame and he's not going to fill his lapses in having a substantive response with silence or stuttering. He's perfectly content to ramble on about non-sequitirs, throw out playground nicknames and just generally defecate out of the anus on his face.
There's a decent percentage of the electorate who love that. There's a decent percentage of the electorate who would recoil with horror at anything Clinton says, regardless of how substantive and on message her answers are. No doubt in my mind she'll "win" the debates. I just doubt that the recognition of her wins will transcend party lines, which they rarely do anyways.
Conservative outlets and voters will praise him. Most mainstream outlets and democratic voters will anoint her the victor. Lather, rinse, repeat... I don't think the debates will matter unless he slips up and drops something insanely offensive.