On the surface, Lady Sovereign and Slim Thug seem to have little in common. She’s a 5-foot-1-inch 19-year-old white rapper from London, England, with a rapid rhyme style typical of U.K. grime. He’s a 6-foot-6-inch 24-year-old black rapper from Houston, with a languid flow typical of the chopped-and-screwed Houston sound. But both find themselves in a similar spot: trying to ride the coattails of breakthrough artists (Dizzee Rascal and Mike Jones) and consolidate the success of their respective scenes.

Lady Sovereign will play her first stateside show this Wednesday at the Knitting Factory. Like M.I.A. and Dizzee’s debuts, it’s going to be overflowing with MP3 bloggers and hardcore indie rap nerds, which, for the moment anyway, comprise the entirety of her U.S. fan base.

In the U.K., however, she’s shaping up to be a genuine star. She recently signed a reported L3,000,000 deal with Universal/Island records; she’s been written up in all the major music magazines and dailies; and she has high profile fans in Mike Skinner (a.k.a. the Streets), Basement Jaxx, grime founder Wiley, and influential BBC Radio 1 Deejay Steve Lamacq.

The attention is well deserved, as Lady Sovereign brings elements to grime that are sorely lacking. She’s a woman, of course, in a male-dominated scene. But more importantly, she’s a talented MC with a barbed wit, a playful flow, and a sense of humor – all of which are mostly absent in grime’s flat, aggressive rhyme style.

On “Random,” one of the early singles that helped to establish her reputation, she brilliantly skewers British MCs for aping American regional rap dialects. “Well I’m right thurr / Naw tell it like, cause I’m right there / Right hurr, naw, right here / Now get off of your churr, I mean chair,” she says, parodying the slurred St. Louis accent. She goes on to criticize British MCs who “get it twisted, start saying ‘cookies’ instead of ‘biscuits.'” Reading the lines doesn’t really do justice to their cleverness. It’s a complex critique of British hip-hop – and one that has the added benefit of being comprehensible to American listeners.

On “Blah, Blah,” a song about jabbering haters, Lady Sovereign raps: “People want to classify me as an Eminem / Boy hear what, I’m a different kind of specimen.” But the truth is, despite her protestations, she is a lot like him – in all the best respects.

Like Eminem, Lady Sovereign is a poster child for the white lower-middle class. She’s what’s known in the London press as a “chav”: a thieving, pot-smoking, gaudy-jewelry-wearing, white city kid with no ambition. It’s an image Sovereign embraces: she smokes cheap cigarettes, inhales fast food, and dresses in baggy Adidas hoodies, tracksuits, and trainers. But it’s a case of managing expectations. Like Eminem, she’s far smarter and more talented than people give her credit for.

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Houston rapper Slim Thug presents himself not as a new face, but as an established talent whose breakthrough has been a long time coming. His major label debut, released under the Neptunes’s Star Trak imprint on Geffen, is titled “Already Platinum.” At one point he raps: “Don’t get me confused with the rest of them dudes / I been the boss down South, I’m just new to a few.”

Mike Jones gets credit for breaking the Houston scene on the national stage with his platinum-selling album “Who Is Mike Jones?” released last April. But Slim Thug’s was the first voice we heard as he delivered the first verse on the breakthrough single “Still Tippin.”

The success of that song has made Houston the new rap hotspot and a possible successor to Atlanta as the seat of the Dirty South. And Slim Thug will certainly help to make the case. But whereas Mike Jones’s album was a strictly Houston affair – with local producers and half-speed chopped-and-screwed versions of most songs – “Already Platinum” is crowded with national talent, perhaps reflecting the heightened expectations for the project.

The lyrics serve as a virtual tour of the Houston rap scene, with special emphasis on all the local fashions: candy-colored Coupe de Villes, Sprewell rims, iced grills, screw (a cough-syrup concoction that is the favored local drink). The sound, however, is Houston once removed. The Neptunes, who handle the lion’s share of the production duties, pay homage to the pitch-slowed local sound, but interpret it through their space-age lens. “I Ain’t Heard of That,” the lead single, is propelled by a slow-motion synth, and the vocals on the title track “Already Platinum” are lightly, almost imperceptibly, screwed.

For a true Houston sound, however, you have to look to tracks by lesser known local producer Mr. Lee: the laidback horn sampling “3 Kings,” featuring Houston legend Bun B. and Atlanta’s T.I., and the syrupy slow “Diamonds.”

This highlights the challenge for rappers so closely aligned with a particular place. Both Lady Sovereign and Slim Thug are representing their scenes, and both are very much products of their environments, but neither is particularly representative. Their success may open the doors for other London and Houston acts, but it will do little to prepare the world for what will follow.

Lady Sovereign plays the Knitting Factory tomorrow night (74 Leonard Street, between Church Street & Broadway, 212-219-3132).