Here's an instance of difference...a major difference. But this is a difference of God, not necessarily Earthly preaching (just go with me a bit). Buddha left his home because he was overwhelmed by human suffering. Jesus' purpose on earth was to save humanity from the wages of its sins. Of course, the path each takes to saving us is drastically different.
But, both, like I've said, when you get right down to it, were concerned with human dignity and how to defeat human suffering. I think this is a proufound connection, even if their paths wind away from one another.
I don't that Jesus set out to "defeat" suffering, rather to end it by reconciling man with God.