Debates never boil down to who is the better or worse president. It boils down to showmanship. A smooth talker can weasel their way out of the toughest questions.
Trump does not perform well in debates. In 2020, he was relying heavily on Biden being unable to string a sentence together, but that backfired.
In 2024, he might be relying on Biden looking old and frail and sounding incoherent. That can backfire again. Biden is doing a lot of practice, and all he needs are to stick to a few strong points that he can memorize. He is preparing to professionally dodge and redirect questions about the border, Afghanistan, the economy and inflation. He is also preparing to attack Trump about January 6th, criminal convictions, court cases etc.
With the mics muted, there is no possibility to interject. This makes it even more critical to stay on point and take their best shot with the time they are given. Moderators will no doubt try to lead Trump into defending himself, and if he takes the bait, he loses.