Depends..
A larger creature would have the advantage of pure size, a smaller one the advantage of speed.
A larger creature simply won't be able to move as quickly as smaller more agile one, that's just the way it works.
Most smaller predators and some large ones as well are pack hunters, they have the advantage of numbers, like Hyenas for one. Working together they can take down some of the larger prey such as Zebra, Buffalo, Antelope etc. The prey has the size but the predators the numbers, and Hyena's wear down their prey but running them to exhaustion, taking turns.
There, numbers win.
But if say a Cheetah which always hunts alone hunts someone like a Dik Dik, size will win. A Cheetah is much stronger and faster then a little Dik Dik.
Dinosaurs most likely could of been the same way, a smaller predator would not take on something as large as an adult Apatosaurus alone, a younger one maybe but an adult could win on size and strength alone.
A pack would have numbers, some to distract, some to ambush etc.
You'll have to go research what Dinosaurs were from what Period and try and work out what they could of hunted and how they did it.
Course, The Land Before Time will have no answers to this, as most of those dinosaurs should not even be existing together.