I honestly think Sheikh Hamza Yusuf speaks in a way that will convince people of the American culture and are familiar with a Christian background... because he not only speaks from an obvious vast amount of knowledge, but also speaks to the heart of people, and is able to teach even born-Muslims to look at their faith in a new way. I can honestly say I've been Muslim since late 2000, and every time, every single time I listen to one of his lectures, I learn something new...and that is something that has continued to this very day.
But if we are talking about people who deal specifically with Christians and so on, as in interfaith dialogues and debates and whatnot... Ahmed Deedat is a good reference for Muslims, and very funny, and has a stunning stage presence... but I would NEVER give one of his debates/lectures to a non-Muslim, because they will walk away feeling like they got punched in the face... wallahi. For stuff like that, if your idea is to give it to a non-Muslim to watch, I would suggest Shabir Ally if you can find something that is good enough quality, or for someone a little more well-known... Jamal Badawi who also has an extremely vast amount of knowledge not only about Judaism and Christianity, but Islam as well, particularly seerah.
Salaam
~Me.