Graphics are -nearly- identical, but you can notice quite a few changes, namely the high-resolution packs. Also the laser sighting no longer looks like a cream beam, it actually looks like a laser sighting.
But, I already found two bugs in the game. That dreaded "lock-up" on split-screen weapon select during mid-mission happens ever so often and if you have a previous save of R6V, you'll get an auto-update rank and so on, yet you will not be able to get the easiest "First Class Private" Achievement.
In SP/Co-Op SP the main character can be of either gender and has an appropriate voice for both, storyline goes before, during and after the R6V storyline.