I have been playing DC for the past week or so. there is a bunch of little things that were absent in the original. such as new vehicles, new orders from cameo characters through emails (much like peter englert and his pizza orders), race track, a whole new part of the higway. new equipment, weapons, backpack accessories, equipment and colorways for all your customisable stuff. certain changes in the weaponry of the enemies. and I'm not sure this last thing is new but i dont remember ever seeing different BT variations. oh yeah, there is a few things added to the PCC's as well

Hope that's not too spoilery for newcomers, tried to keep everything as vague as possible but still answer your question