Set on Manhattan's Upper West Side within bagel-throwing distance of the lox counter at Zabar's, Bad Jews delivers handily on its title: Between Daphna (Tracee Chimo) and her antagonistic first cousin, Liam (Boardwalk Empire's Michael Zegen), it's a toss-up who's worse and worser in Joshua Harmon's lively little comedy of hostility and intrafamily kvetching now on the small stage at the Roundabout Underground through Dec. 30. Daphna, who changed her name from Diana, plans to move to Israel when she graduates from Vassar and sets great store by ritual and tradition. By certain Talmudic standards, she's the ''better'' member of the tribe; she's also resentful, hurtful, judgmental, and all around a deeply unpleasant young woman. (The terrific Chimo, previously an Off Broadway wow in Bachelorette and Circle Mirror Transformation, is a dynamo of motion and dyspeptic energy. Even her rambling, curly hair exudes uncombed anger.) And Liam is, by some rabbinic measures, the more wayward of the two, having aggressively rejected his Jewishness. (At a key moment, Zegen produces one hell of a self-hating-Jew scream.)
Liam arrives late from out of town for the funeral of their grandfather a holocaust survivor with all the emotional baggage that leaves behind for the living. Like Daphna, he crashes at the cramped studio apartment of his conflict-phobic brother, Jonah (Compliance's Philip Ettinger) but Liam also brings along his gentile girlfriend, Melody (Molly Ranson, late of the Off Broadway Carrie revival). Clearly, the room isn't big enough for the four of them, and the apartment can barely contain the nosh-fueled verbal slug-fest between Daphna and Liam, choreographed with excellent stomping and crawling over makeshift air mattresses by director Daniel Aukin. The other two players tend to recede into the background. Jonah's refusal to engage with anyone in the room borders on mental disability, while Ranson displays bland, blond pilgrim cheer as Melody, calmly occupying her time with her smartphone while her boyfriend bellows.
Okay, so how does one define ''bad'' or ''Jew''? A rising playwright currently studying at Juilliard, Harmon is less successful at suggesting new ways to look at old debates than he is at giving his characters some zingy ways to push each other's buttons. B
(Tickets: roundabouttheatre.org or 212-719-1300)