They are both great bands, but Metallica are one of the best bands in history, period.
People just sound dumb when they say "Metallica sold out after the Black album".
Sad But True, Wherever I May Roam,The Unforgiven, Nothing Else Matters, Hero Of The Day, Bleeding Me, King Nothing, Fuel, I disappear, Broken Beat And Scarred, Suicide & Redemption, My Apocalypse, The Memory Remains, Turn The Page(great version) etc.......etc....... All very good songs(some legendary)
I love some early Metallica just like anyone else, but who the fuck wants to write and perform the same type of shit their whole life!! If you are an honest artist you will try to stretch out & write in different styles.
By doing this, some things will be hit or miss, but that is part of an honest journey as an artist or band.
FUCK what fans think. You will loose some & gain some, but it shouldn't be about the fans anyway.
The people that sell out and are fake(or just have really low IQ's) are those that claim they can listen to, or perform & write the same style of shit over & over. Bands who do this are just "phoning it in" or are just not talented or brave enough to change.
As for Megadeth, I love a bunch of their tunes and Dave's voice sounds great on record. He is an amazing rhythm player and has written some iconic metal riffs & songs