Lincoln's "House Divided" speech, which talks a lot about the Dred Scott decision, aimed to convince Republicans of the real danger that slavery would soon be legal everywhere. Frederick Douglass' earlier response to the Supreme Court case took a different approach.

He starts out along similar lines:

It is a fitting time to take an observation to ascertain where we are, and what our prospects are. (Source)

However, although he acknowledges how strong the institution of slavery is at that point in time, he's confident that in time, it will be gone. He points out the progress of the abolitionist movement:

Take this fact—for it is a fact—the anti-slavery movement has, from first to last, suffered no abatement. It has gone forth in all directions, and is now felt in the remotest extremities of the Republic… Politicians who cursed it, now defend it; ministers, once dumb, now speak in its praise; and presses, which once flamed with hot denunciations against it, now surround the sacred cause as by a wall of living fire. (Source)

Good point, Frederick D. In directly addressing the Dred Scott ruling, he does not despair:

I have no fear that the National Conscience will be put to sleep by such an open, glaring, and scandalous tissue of lies as that decision is, and has been, over and over, shown to be…By all the laws of nature, civilization, and of progress, slavery is a doomed system. Not all the skill of politicians, North and South, not all the sophistries of Judges, not all the fulminations of a corrupt press, not all the hypocritical prayers, or the hypocritical refusals to pray of a hollow-hearted priesthood, not all the devices of sin and Satan, can save the vile thing from extermination. (Source)

He also points out that—despite what people like Justice Taney have claimed—he doesn't see how the Constitution supports slavery and the prohibition of citizenship for Black, even bringing in historical fact to support his assertion. Imagine that, using evidence, no wonder this guy did well.

Douglass' essential point is that it's inevitable that slavery will die out. It's wrong, and people are increasingly figuring that out, so there's no way the institution will continue. People aren't that completely awful. Lincoln also says in his speech that he doesn't think the union will dissolve, but Douglass takes it further and sees the end of the slavery altogether.

Abraham Lincoln is a pretty good speech writer, but Douglass is a lot more poetic and emotional in his speech. He doesn't shy away from lines that kind of make you want pump your fist in the air a little bit.