I do agree with Ken
in the 90's it was the mainstream wave to have a "dirty" sound in death metal and OL weren't exactly progressive those days.they were a middle eastern death metal band.
Mabool should've been recorded clean because it has a lot of progressive elements and plenty of acoustic instuments like paino, buzuki and oud...it just wouldn't sound right when it's dirty
Nowdays it's more and more common to have a "clean" sound in death metal because it is getting more progressive over time.
A bad example IMO of using a clean sound is BLOODBATH...who are supposed to be a homage to oldschool swedish death metal and the clean sound(courtesy of Dan Swanö) just doesn't sit there well.
this is my opinion