James might have a cleaner voice and is technically a better singer but that's still not saying much. Not to mention, although Megadeth has had some questionable albums, they've at least kept the metal banner high, and Dystopia can go toe-to-toe with Megadeth's best classic works in my opinion. Metallica fell off something fierce after Ride the Lightning; I find Puppets rather dull and even dreadful at times, and Metallica had this bizarre tendency to get into bluesy, midtempo rock territory even with their big hits, which is severely off-putting to me. But with Megadeth I can at least count on some actual metal. (And the less said about Load, ReLoad, St. Anger, the better)
But, since this is about Puppets... I dunno, Rust in Peace just blows it out of the water. Both are pretty metal, but Rust just has this sharper edge to it, it feels angrier and heavier, and Dave's voice is a part of that.