Well last year was pretty well a career year for O'Brien with 20 points. Not sure you can count on him for output anywhere close to that again. He's pretty much just a decent PIM option.
I'd give Barrie a go as he just might get a shot at the top power play and could be a hit out of the gates. With the shortened season you just gotta gamble and hope you strike on someone who is hot out of the gates. If Barrie is a dud just switch him out for someone else. Maybe you end up using O'Brien just for the PIM while you wait for a hot option to come up on the waiver wire.