In comparing Sarah Kemble Knight's The Journal of Madame Knight with The Account of Mary Rowlandson and Other Indian Captivity Narratives, use three quotes to demonstrate a preference for one or the other writer. The choice of writer is irrelevant, as long as you use three quotes to prove your stand.

If you choose to write about The Journal of Madame Knight, you might want to mention that Sarah Kemble Knight's writing is lively and personable. While describing the travails she encounters getting around colonial New England, she narrates her travels with a keen sense of description and a wry sense of humor.
For example, in the following passage, she describes crossing a river in Rhode Island:

"The Post got a Ladd and Cannoo to carry me to tother side, and hee rid thro’ and Led my hors. The Cannoo was very small and shallow, so that when we were in she seem’d redy to take in water, which greatly terrified mee, and caused me to be very circumspect, sitting with my hands fast on each side, my eyes stedy, not daring so much as to lodg my tongue a hair’s breadth more on one side of my mouth then tother, nor so much as think on Lott’s wife, for a wry thought would have oversett our wherey:"

In this passage, she conveys her predicament with humor, as she says that even moving her tongue might cause the canoe to tip over. She also says that even thinking about Lott's wife (a Biblical story) would have upset her canoe, which is obviously humorous because a thought cannot upset a boat.
Another quote you could use to demonstrate your preference for Knight describes how, later, in looking at the moon above the countryside, she is moved and writes a poem:

"But being got to the Top, was there amply recompenced with the friendly Appearance of the Kind Conductress of the night, Just then Advancing above the Horisontall Line. The Raptures wch the Sight of that fair Planett produced in mee, caused mee, for the Moment, to forgett my present wearyness and past toils; and Inspir’d me for most of the remaining way with very divirting tho’ts, some of which, with the other Occurances of the day, I reserved to note down when I should come to my Stage. My tho’ts on the sight of the moon were to this purpose:
Fair Cynthia, all the Homage that I may Unto a Creature, unto thee I pay/In Lonesome woods to meet so kind a guide,/To Mee’s more worth than all the world beside."

The moon, which she refers to as the "Kind Conductress of the night," causes her to forget her weariness in traveling. She is moved to write down her thoughts about the moon, which she also refers to as Cynthia, using an allusion to the Greek goddess of the moon. This type of poetic writing has a unique voice and conveys Knight's personality and style.
One approach you could consider for your third example would be to use a quote from The Account of Mary Rowlandson and Other Indian Captivity Narratives to demonstrate why you prefer Knight. While Mary Rowlandson's narrative is filled with the excitement of conveying an attack by Native Americans, you might find it has a wooden quality. For example, even when Native Americans are attacking her house, her account has a stilted quality to it:




"We had six stout dogs belonging to our garrison, but none of them would stir, though another time, if any Indian had come to the door, they were ready to fly upon him and tear him down. The Lord hereby would make us the more acknowledge His hand, and to see that our help is always in Him. But out we must go, the fire increasing, and coming along behind us, roaring, and the Indians gaping before us with their guns, spears, and hatchets to devour us."

Rowlandson's narrative also has a religious overlay, so she attributes what happens to divine intervention. She narrates a very dramatic episode with an economy of words, and the writing does not provide the reader with access to her innermost thoughts and feelings the way that Knight's writing does.