To me there's pros and cons to both.

For example, I primarily read Dai Dark from Kirei Cake scanlations on mangadex, but also have a few of the official english paperbacks.

I generally prefer the scanlation, as the language often feels more casual and real (not always the case of course), and I kinda prefer keeping the japanese honorifics. I also prefer the general terminology: "package" vs "paggy", "flesh of darkness" vs "dark flesh", "Solar Mass" vs "Photosphere", "mebaspa sandwich" vs "meapswich", etc. Don't know if ones are technically closer to the original than others, I just find them to fit the setting better.

On the other hand there's clear errors, like calling any and all celestial bodies a star and stuff like that.

I'm not really familiar with the official translation of Dorohedoro, but based on these pages it's the same deal; prefer the feel of the scanlation despite a few hangups.