Which one is more powerful?
In terms of destructive power, I presume...
Both were shown to deal great damage to, and assumed capable of completely destroy, the Enterprise.
I rather doubt the
Narada would have been capable of that. She made short work of unshielded starships, but when Pike had shields up, they made a significant difference: the
Enterprise took very light casualties compared with the likewise shielded
Kelvin, still retained the ability to fire back (the
Kelvin lost that ability twice in the first battle, although was very quick to recover), and still retained the ability to go to warp if need be.
In turn, there is no indication that the
Narada would have had any means of defending herself. Neither of the captains of the
Kelvin fired at Nero's ship - both only fired at his missiles. Pike would not have been that timid. And the shields of the
Narada were apparently a joke - they didn't even stop Kirk and Spock from beaming aboard (and yes, they were up, as Chekov later makes note of them going down). All that the giant mining rig has to her defense was her sheer bulk. Although there was plenty of it!
In comparison, the
Vengeance decisively took out Kirk's weapons, eliminated his ability to go to warp or even move around at impulse, and demonstrated immunity to Kirk's weapons (Marcus had too little crew to conduct effective repairs with, yet never lost any functions until Scotty's sabotage). Which is only to be expected, as this ship would be designed specifically with
Enterprise-level opponents in mind, whereas the
Narada apparently was never designed to go to battle of any sort...
In STID the Enterprise seemed to be more damaged and more quickly.
Even more so than the poor
Kelvin... And that was before Marcus brought his big guns to play!
In ST2009 the Narada quickly destroyed several ships (similar to the Enterprise) but that could be a particular tactical condition.
Heck, it could even be another application of the red matter he had aboard - a series of space mines to do hurting well beyond the abilities of the actual ship!
But the dialogue heavily suggests that those destroyed ships did not have their shields raised, as it took a shouting match on the bridge to get Pike to raise his. And we know that the mightiest will fall if their shields aren't up.
But she was disabled by the Kelvin.
Whose shields were up. Or at least her crew was convinced that they were up, and dumbfounded that the ship was still taking damage as if unshielded.
And at that point, Nero was confused, not knowing where and when he was and who he was fighting, and not really prepared to fight anybody but Spock and his tiny vessel. When defeating the cadet ships over Vulcan, he had had a quarter of a century to prepare!
I don't see a big discrepancy there, really. The
Narada was a powerful mining rig, but not much of a warship. But Nero was cunning and ruthless, and waged information warfare (torturing people for important codes, sending false messages, jamming communications and other connections). He didn't need a badass ship.
Marcus OTOH needed that very thing, for his war against the Klingons. And he got what he wanted.
Timo Saloniemi