Did you even listen past the first 10 seconds? Even his softer vocals are better than Tool's. And he does both in the same song.
You can take the 'there's no comparing' them route, but if you do, well, there's no comparison. They can't hold his jockstrap.
Also notice how other even shittier bands completely fall away in comparing too: NiN, SoAD (it's insulting even putting Slipknot in same post), and all the rest of the shit aren't even in the same universe. After listening to Opeth, you're forever spoiled.