Pros of squares: One big pro, if you damage one you can just remove it, and replace it and the damage is gone in 20 minutes. This only works if you buy over the amount you will need so you will have extra because they discontinue these patterns faster than you can imagine. Lay extra flat and in a warm spot.
Cons of Squares: you do have those seams. If the instal is done right the seams are not that visible after you get used to them.
Pros and cons of sheet are pretty straight forward, no seams, more labor to install, and one ding and its there for the duration, (in most cases).
Too many people buy cheap tile squares. I like thick tile, I like the sticky side to hold the tile suspended after your finger sticks to the sticky side. That 1/64 inch thick tile from overseas and sorry messy glue make for a sorry install job.