In a car which has similar engine but different transmission, let's say a Corolla Axio auto and manual, the manual will be faster
This is because the auto gearbox is heavier than manual gearbox, and due to the nature of the auto gearbox, there is more power loss in its mechanisms compared to a manual. Hence less power actually reaches the wheels compared to a manual
This comparison is only valid for normal run of the mill automatic gearbox that most cars have nowadays, not those new DCT and whatever