well...i like the sound they got on CI. GHUA was heavier, but then again CI is way more old-school musically as opposed to GHUA being almost modern in character, so the low-gain CI production is definitely fitting. imho.
besides, except for reign in blood and everything from diabolus in musica onwards pretty much every slayer record sound like shit. even show no mercy sounded better than most of the stuff they've done after that. hell awaits sounds awful (ok, that was like what, 85? so who cares...even though metallica RTL kicks the shit out of HA regarding sound), and as for the all-mids comment, have you guys ever listened to seasons or south of heaven??? now THAT's all mids. CI is almost scooped sounding in comparison...that, and the music is better. imho.