And what "work" will you be doing? I can't imagine they will let you do anything substantive. So what will you be doing? Working in the file room? Making copies?
Its a bad idea in my opinion to work for either one of these places as a 0L. Take your summer off and enjoy yourself. You won't really be doing yourself any favors by working at either place. Some people may know your name, so you might help yourself out slightly in terms of getting summer employment there later. But you could also get a bad rep there and screw yourself out of summer employment at either place. If you're dead set on wasting your time, I'd work at the place you feel more comfortable with the people.