3D is better for giantesses because you don't have to worry about the belly, which is often the worst part in 3D. You can also show the trip down and even create a good environment for the stomach in 3D, with casual vore being amazing since all you do is, after the swallowing scene, you just add some casualness, and it looks so good. For example, this video is peak giantess.
There is one benefit I think 3D has over 2D for same size vore, which is that longer digestion scenes are much easier to make in 3D, as you can have the belly shrink over time and go from big and hard to sloshy and small over a long period of time for a fraction of the effort. You can also have the pred do shit well, they churn their prey up. However, I've never seen anyone do this, so it's a moot point.
I know that this could all be possible in 2D, but it would take so much work that no one could feasibly do it on their own.