The sporting world has contributed to a match made in fashion heaven: Victoria Beckham and Los Angeles. Ms. Beckham — along with her enormous sunglasses and creative wardrobe — will be spending more time on the West Coast now that her husband, the soccer megastar David Beckham, has signed to play for the Los Angeles Galaxy.

It couldn’t be a better fit. L.A. style is based on three things: celebrities, jeans, and celebrities in jeans.

Ms. Beckham has positioned herself in the global press as a fashion leader (regardless of whether she is or not). She has launched multiple lines of denim — which she will surely wear to gatherings of every sort, as per the local custom.

It’s such a natural pairing that the mind reels at the thought of the opposite: Ms. Beckham and New York? Couldn’t happen.

In terms of style and shopping, New York and Los Angeles might as well be in different countries. “It’s like Rosie and Donald. They really do hate each other,” the owner of the boutique Kitson, Fraser Ross, said. “When someone walks in the store wearing all black, you know they’re from the East Coast. You know there’s a tourist in the store.”

Mr. Ross’s 7-year-old shop on Robertson Boulevard has become a hot spot where shopping celebrities — laden with the store’s signature blue bags — are snapped by photographers. As a result, the store has become in part a tourist attraction on the order of an amusement park. “They want to go where the stars shop,” Mr. Ross said.

That makes for one of the city’s most fundamental differences from New York. “L.A. is celebrity driven, but in New York, you have the socialites who are setting the style,” the publisher of the “Where to Wear” shopping guides, Jill Fairchild, said. “Designers always want a Julia Roberts, but to have the socialites in the front row of a fashion show is an enormous value.”

When those socialites are photographed at fashion shows, they are typically well turned out, as opposed to celebrities who turn out in jeans no matter the occasion.

It’s a distinction that ripples across the fashion spectrum. People who travel between the two cities frequently, such as Julie Zipperer, vice president for sales of Scanty, an upscale loungewear brand, see the differences first hand. “In L.A., you can go to a cocktail party in flip-flops. In New York, everyone is dressed to the nines.” Ms. Zipperer said. “It’s tailored and well put together. Ladies get their hair blown out. They’re still hippies in California.”

The stereotypes of New Yorkers wearing black and Los Angelinos wearing jeans even hold up in the maternity market. During pregnancies, women on both coasts want to maintain their personal style, according to Rebecca Matthias, the founder and creative director of Mothers Work, which owns the boutique chain A Pea in the Pod. “How it translates to what they buy is that women in Los Angles will buy the 7 for All Mankind jeans. In New York they buy Diane Von Furstenburg wrap dresses,” she said.

Ms. Matthias also pointed to comparative sales of basic black pants in two equivalent A Pea in the Pod locations. During a recent one-month period in Los Angeles. 16 pairs were sold. In New York, 116 pairs.

Understanding the consumer is key for Barbara Kramer, the cofounder of the Designers & Agents trade shows that take place 10 times a year — five in Los Angeles and five in New York. Vendors of clothing, jewelry, and accessories are selected by committee for the shows; buyers in each market then place orders to fill their shelves. “We could make the shows the same, but the retailers have such different aspects,” Ms. Kramer said. “The California shows tend to be younger and more unisex. The John Varvatos Converse line does well there. If a brand is urban, sophisticated, and tailored, we put it in the New York show.”

The casual lifestyle of California has made certain brands and trends stick. “L.A. has pushed the $200 to $300 jeans trend,” Ms. Zipperer said.

At Kitson, Mr. Ross finds great success with the brand Great China Wall, which makes graphic tank tops for $245 and hoodies for about $1,000. “They’re based in L.A. They don’t do that much in New York,” he said.

The West Coast demand for a relaxed, modern look has also made L.A. an attractive market for international brands looking for a foothold in America. Not only that, the vast real estate options there — as opposed to Manhattan — provide the opportunity to enter the market without putting the entire enterprise in jeopardy. The French label Zadig & Voltaire, which sells a Parisian version of affordable luxury, opened its first American location in Los Angeles after spending two years searching for the right space in Manhattan. Price was a factor in negotiating, but choosing from the limited supply of space in the neighborhoods they wanted — SoHo and the Meatpacking District — proved the biggest challenge. In the end, the company looked to the West Coast.

“We found good reasons to be in L.A.,” the CEO of Zadig & Voltaire, Al Cadosch, said. “If we go to L.A., we’ll be worn by celebrities, and the brand will have the glamour it has in France. L.A. is more about what you want to wear, not what you have to wear.”

Though Mr. Cadosch and the design team are still looking for a space in Manhattan, they’re in no hurry: “We have the money. We have the brand. I don’t need to make a mistake in New York.”

Likewise, the Barcelona-based Mango chose Orange County’s South Coast Plaza to launch its American retail efforts. By the time it opens in Manhattan at the end of the year, Mango will have nearly 1,000 stores worldwide and more than 10 stores in America.

On the upper end of the fashion spectrum, L.A. real estate benefits from its large spaces and freestanding stores. “You drive to Robertson Boulevard, Montana Street in Brentwood, Malibu, and now Melrose is popular,” Ms. Zipperer said. Indeed, Melrose has a growing New York presence, with a Carolina Herrera boutique that opened in July. Oscar de la Renta will open a store this year.

The individual shops also allow for the freedom to get creative. Max and Lubov Azria commissioned artist Patrick Dougherty to create an outdoor art installation on the MaxAzria boutique on Melrose Avenue. The result is a swirling nest of twigs that draws attention to the shop. Ms. Azria, creative director of the BCBGMAXAZRIA and MaxAzria collections, intended the sculpture to extend the concept behind the brand. “The whole DNA of MaxAzria is about the artist,” she said. “We see so much art that is inside a building. This sculpture is outside — we couldn’t do this in New York.”

Even so, Ms. Azria knows where fashion lives. “In New York, the shoppers are connoisseurs. They make investments in clothing,” she said. “In L.A., they’re playing with clothes. They take more risk, and there’s more bad fashion.”

She’s not shy about pointing the finger. “Kitson needs to get a fashion citation. It creates fashion victims. The Uggs, the T-shirts, the Nicole Richie,” she said. “You just want to say, ‘Please. Enough.'”

But with Ms. Beckham in town, “enough” is surely just the beginning.