I suspect the Spear can separate Angel and coin, effectively taking the Angel out of the game. Same type of energy of creation, so not destruction. The Eye is a different type of energy of the same magnitude so more likely to destroy. The Spear could be used without the type of blowback the use of the Eye would engender. Who knows, it might even reverse the Fallen status.
Wouldn’t that be terrifying for Nicky and Anduriel? Is that why he was after the Spear
I don't know if even the Eye could destroy one... I would guess it depends on who made the Coin. If TWG - likely indestructible, even to the Eye. They speak of the Swords being able to pierce even Titanic Bronze, and they are wielded by humans, though it might take a more powerful wielder to kill Ethniu with it, but if a Sword could destroy a coin.,.. I have to think that it would have been done at some point.
But.. who DID make the Coins? The idea passes they are NOT prisons for the Denarians, but the Denarians or the like MADE them. They are to be distributed among humans to gain power and corrupt humans. The Denarians are using them as a conduit to get into the world, and go voluntarily. So the Spear won't separate Damned and denarius - they want to be there, though maybe they can be driven out. I think the Fallen status remains. I think that status can only be lifted by TWG. Possibly it could banish THAT Fallen from a Coin, and leave that Fallen unable to contact Earth. But maybe another Fallen can then hop into the Coin. "Lasciel, you are out - Belial, do you want to try?"
There's a few supposed Spears out there, claiming to be the real one. Unconquerable? Then I guess the one the Holy Roman Empire had wasn't real.... some also say the power is in seeing the future, not necessarily winning... else, wouldn't Harry have just had to show up and stick it in Ethniu? Harry can't be conquered then, right? But maybe Harry thinks that, and the Spear telepathically tells him, "Nope. Try it and die. Come up with a Plan B" but doesn;'t tell him what to do.