I would like to transfer photos from one computer to another, but I would like to maintain the originals (most of them are re-touched), faces information, gps coordinates, whether the image has been hidden, and it's rating. I know that transferring using the built in sharing mechanism will remove this detail, so is there a workaround?
There is a (paid) utility, it's called iPhoto library manager. From the description on the website:
Copy photos from one library to another while retaining titles, comments, keywords, ratings, and dates
Generally speaking, this is metadata that's stored in the iPhoto Library itself; only the GPS coordinates are added to the photos’ file(s). So really, the only way to preserve that would be to either copy the library itself, or use the utility Agos recommended.
Especially when you mention you want to maintain originals + the retouched versions; that's something that the iPhoto Library itself can only maintain.
Explore ~/Pictures/iPhoto Library. Right-click on it and choose "Show Package Contents," that will give you access to the various files, with metadata in them, as well as the "Originals" and "Modified" folders. You can pull the originals out of the originals folder, but I think the metadata is stored among the various other files scattered about.