In The People's History of the United States, Howard Zinn discusses the issues of slavery in chapter 9, entitled "Slavery without Submission, Emancipation without Freedom."
He begins the chapter with a discussion of three notable slave rebellions within the United States, including Nat Turner's in Virginia. Zinn uses this discussion to introduce a question that was popularly discussed during the early-to-mid-1800s before emancipation. Many abolitionists at the time criticized slave rebellions, saying that they hurt the cause for abolition rather than helped it. In fact, following Nat Turner's rebellion, the state of Virginia increased security measures to defend itself from potential roving armies of angry slaves—despite the likelihood that most slaves chose instead to abscond.
Depending on your view, one could argue that running away rather than rebelling is equal to resistance. Resistance implies a kind of peaceful refusal to accept the oppressive forces of slavery, and absconding was the most common form of this resistance. According to Zinn, "During the 1850s about a thousand slaves a year escaped into the North, Canada, and Mexico." This statistic shows that running was the most popular form of resistance to slavery, at least among the slave population.
On the outside, black Northerners advocated for the abolition of slavery, including David Walker, whom Zinn mentions directly as an example of the kind of advocacy that enraged Southern slave-owners. Frederick Douglas emerged as an abolitionist hero of sorts, dedicating his life to publicly telling his story and denouncing the horror of slavery as a stain on the entire nation—not just the South.
With support from white abolitionists who helped spread the abolitionist message to audiences who would otherwise not receive it, the abolitionist movement was instrumental in encouraging emancipation. Based on Zinn's discussion in this chapter, one could certainly argue that public resistance was more effective in the abolition of slavery than violent slave rebellions.