The guitars on Appetite have way less gain, and I'm pretty sure Slash did a lot less doubling than Hetfield did.
Mike Clink has a real fetish for treble, everything should sound as glassy and bright as possible for him. You can really hear this on Justice, there is no bottom end anywhere in that album, even the kick drum sounds like Lars is tapping on a beer bottle.
When you put tons of high end on a heavily distorted guitar you bring out lots of the upper register harmonics, which sounds pretty cool. When you do it on a bass you don't get quite the same results, and we loose the very thing we are supposed to be doing: providing solid low end to anchor the song.
Its not an issue on Appetite because there just isn't that much guitar, but with Justice Hetfield was trying to get his signature Wall o' Mesa guitar tone. With the low end guts of the bass track leeched out there was very little to set Jason apart.
Had he been allowed to expiriment more as a player Jason probably would have been more prominent, but he was confined to doubling James by the rest of the band members, thus Justice's bass track is lost to the ages.
My old guitarist and I had an inside joke: What do Santa Claus, The Easter Bunny and talented, reliable drummers without drug problems listen to when they hang out?
The bass track from And Justice for All
