1/4 sheet vibrating sanders go in small circles. If you leave it in one place and pull it off the work after a real quick buzz, you can see the marks. The DA allows the pad to rotate while vibrating so that those mini circular marks are eliminated. Some DA sanders you can lock up so they become a single action just like the 1/4 sheet.
BTW, I have a 1/4 sheet Makita fitted with a round pad so I can use 6" self adhesive discs. I like that 10 times over fussing with the clamps which always seem bot get sanded smooth by the paper. For that reason alone, buy the round sander and avoid hood and loop if you can as the paper is way more expensive. I buy rolls of round sheets with up to a 100 sheets to a roll for like 10 bucks.