Cons:
True "high compression" for a game like BioShock Infinite (which uses the Unreal Engine 3) doesn't exist. The repackers achieve small file sizes by removing assets (like multi-language packs) or re-encoding videos to potato quality. They cannot magically compress 35GB of complex geometry and physics into 2GB without destroying the game.
While the file size reduction is highly tempting, grabbing random repacks from unverified sources online introduces serious risks to your computer.
"Highly compressed" files are game packages that have been shrunk down using advanced data algorithms (like LZMA or custom repacking scripts).