Megadeth, by a long long LONG shot
The Resurrection
Both bands basically sucked after they left thrash metal.
I don't agree... you can dislike the music Megadeth made once out of the thrash scene, but they never sacrificed quality on-stage from their music because of it.
Metallica, on the other hand, has de-evolved into even not knowing how to play a guitar solo (even those that were written by themselves!)