I think it's totally a matter of preference. I don't think a buried knot is any more secure than taking a few tiny stitches, maybe less so. As I recall, Leah Day said she buried knots because she prefers the way it looks, not because it's more secure. On all the FMQ videos I've seen, people have done the stitches rather than burying knots.
Burying knots is the way you start and stop in hand quilting. You make your quilters knot, ending it about 1/4" above the surface of the quilt. You then slip the needle into the batting, and bring it up about 1/2" away, and use your thumbnail to help ease the fabric over the knot while pulling the thread, until the knot slips through the fabric. You could probably find a youtube video that shows the process. When I FMQ, I bring the bottom thread up, knot both threads together on the top of the quilt, thread the two threads into the cheater needle, and proceed the same way as with hand quilting.