I apologize if this is already answered somewhere but I'm curious what exactly a fitgirl repack is? I know it's a pirated version of a game but like is it just an installer or something? And if you imported the game into steam for example can you be "banned" or VAT (idr the term)
The compression was already explained - I would add that if you're not deep into scene groups, popular repackers are in general a safe choice, i.e. no malware included. Of course it's never 100% safe, but in my opinion safer than picking from a list of torrents what could be the scene release.
I never had issues with fitgirl and Dodi, maybe other users can drop some more names that have proven to be reliable over a long time.