Douglas may be very different than Abe (one's short, the other's tall), but when you compare Davis to Abe, they're so different that they make Douglas and Lincoln look like brothers.
Compare Abe's career to Davis's: on one hand, we have Abe, who eventually became a lawyer after years of ax-wielding, served a couple of terms in the state legislature, and then one term in the US Congress.
And on the other hand, we have Davis, probably the most "accomplished Southern politician in America" (10.71). Davis fought in the Mexican-American War, was governor of Mississippi, served in the Senate, and also in President Franklin Pierce's cabinet as the Secretary of War.
So if there's going to be a war between the states (Spoiler Alert: there is), who would you want on your side? The new guy with the funny hat (Abe) or the guy who has been in war before and knows the Commander-in-Chief?
Davis may have the skills for war, but he also has terrible, terrible ideas. The narrator describes Davis as "proslavery" (10.71), but he's really pro-vampire, which is just as bad. When Abe and friends go to assassinate Davis, Davis lays out his reasoning. Vampires are strong and it's better to be on the winning side, so… (10.122). Wow. Way to stand up for what's right, buddy.
By contrast, Abe is sticking with a very hard fight because it's the right thing to do. Even Davis recognizes Abe's commitment: "and dedicated, my Lord! Coming all the way down here just to kill a man! Leaving your family alone and unprotected in Springfield […] no, sir, let no man speak ill of your convictions" (10.117). By contrast, Davis's only conviction here is that white people are better than black people and that he should work with vampires in order to save himself. Sounds like a real winner.