No evidence these two are not exactly the same in terms of powerset; there was no conscious decision to make MOS Supes less powerful. What Routh Superman has is a lot more experience; that could be the deciding factor.
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"I'm not smart so much as I am not dumb." - Harlan Ellison
Actually I just re-watched the World engine scene, and it's far more impressive than I thought. The gravity beam was flattening cars and collapsing entire skyscrapers with ease, and Superman still overpowered it while weakened. That's damn impressive. It certainly blows anything Hulk and Thor did in their films out of the water. I still think the island feat is superior but MoS is stronger than I thought.