There's so much new writing on the fringe that you might be forgiven for thinking a new play festival was gilding the lily. But one great advantage of the London New Play Festival is that it gives the work a clear context and allows audiences to compare how very differently young writers are using the stage. So far, this year's festival has done this ingeniously, launching plays in pairs that have themes in common, but whose styles contrast enormously.

The international strand of the festival kicks off at the Gate with two wonderfully complementary plays. There is a thematic link - both celebrate people rising above their dowdy circumstances - but they make completely different use of the nature of theatre. Wendy Hammond's Julie Johnson falls firmly within the naturalistic tradition and uses the intimate Gate stage to draw you into her characters' lives, while Two Horsemen by 'Biyi Bandele- Thomas is emphatically theatrical, playing with stage reality to brilliant effect. Both playwrights succeed on their own terms in writing sympathetically about people shortchanged by life.

Hammond's Julie Johnson (from New Jersey) is as modestly titled as it is written. The play tells the story of Julie Johnson, a Mum from small-town America, and her struggle to make something of herself. Julie left high school with no qualifications and has never had a job but, as we meet her, she is on the verge of booking up for an evening class on computer science (so nervous is she about her husband's reaction that she hides her computer magazines beneath the mat.) She persuades her high-school chum, Claire, to go with her for moral support. Soon Julie has fallen passionately in love with learning - and also with Claire. The play charts their progress as students and as lovers, encumbered by small-town mores, their own inhibitions and Julie's kids.

That's it. It's a simple story, and Hammond's writing is low-key, but her play is lovingly crafted and compassionate. She writes well about nothing much - there are scenes where very little happens, yet the story moves forward. At times she even chooses to avoid crunch dramatic scenes - we never see the love-making, for instance - and to find another way of communicating the impact of the scene.

In places this sparseness backfires: there's a reference to Julie's daughter's anorexia that seems gratuitous. But Hammond writes winningly about the imagination and effort Julie needed to up-end her life. Her play demands, and gets, detailed direction (Phil Setren) and performances of emotional authenticity. Melee Hutton is compelling as the dogged, passionate Julie and is well matched by Susannah Doyle's fun-loving Claire.

In Two Horsemen, 'Biyi Bandele-Thomas (from Nigeria) also writes sympathetically about imaginative escape from drudgery. Two men in a hut while away the time by talking. They say they are street-sweepers, but gradually they slither away from reality, swapping identities and repeating passages of dialogue until you have no idea who they are, what is the truth and whether they are alive or dead.

Bandele-Thomas's writing is exciting, enigmatic and disturbing - like Beckett and Pinter, he manages to use dramatic dialogue to create an unsettling slippery world and in Roxana Silbert's production Colin McFarlane and Leo Wringer feel their way through their sliding scale of relationships with great skill, now brotherly, now menacing.

Trestle Theatre Company's Window Dressing (Holland Park Theatre) also uses dramatic form to explore the way people escape from the mundane. Here twins separated at birth meet by accident and decide to make some money by telling their story on a tacky TV chat show. But the show, going for the emotional jackpot, also finds the mother who abandoned them - with awful consequences.

As ever, Trestle makes ingenious use of masks. The key characters are masked, while those in the TV world are unmasked, but less real. So far, so good - but they then add several more layers: they use video, bring in the paranormal and come at the whole story from the framework of the TV programme. This is too much baggage. The sub-plot about the greasy chat-show host detracts from the impact of the main story, and, since the unmasked characters talk and the masked don't, you find yourself missing the nuances of emotion that dialogue can express when the sisters meet. It's an ambitious, topical show, dealing with media exploitation, but it's saddled with too many complications.

For New Play Festival details see London listings.

Trestle at the Key, Sudbury, 5 and 6 Aug; Edinburgh

Festival, 15-27 Aug