Phillis Wheatley left no narrative of her life, though multiple biographers, notably Margareta Matilda Odell, recorded her life story as a preface to her published poems. Olaudah Equiano, on the other hand, wrote a detailed, multi-volume narrative of his life, beginning with his time in Africa and including descriptions of the dreadful Middle Passage and the horrors of slavery. Beyond this, there are many similarities in their lives.
Both were born in Africa and brought to the Americas in the 1760s. Both place a great emphasis on Christianity, which they see as a vehicle to moral improvement. Wheatley even, in one of her poems, writes that it was a "mercy" that brought her from her "pagan land" so that she could be instructed in Christianity. Equiano, who catalogs the horrors of the Middle Passage in memorable prose, did not share this view.
Both attained considerable popularity as writers during their own time, though Equiano's narrative, unlike Wheatley's poems, was specifically used to support the growing antislavery movement. But the most significant difference is that Wheatley, a poet, did not publish a narrative along the lines of Equiano.