LONDON, England (CNN) -- News that acerbic British judge Simon Cowell is quitting the hugely popular talent show, "American Idol," has led to intense speculation as to whether the show can survive without him.
Cowell is the undisputed star of the show, which until recently pulled in 30 million American viewers. Fans love his brusque and brutally honest appraisal of the hopefuls.
But Simon, it seems, plans to shift format and launch his equally successful UK show, "The X Factor," in the United States.
Cowell is a judge and executive producer on "X Factor," the British show he created in 2004. Last series it drew in a peak British TV audience of 19.1 million, according to the ITV network that airs the show.
So what can viewers Stateside expect from "X Factor"?
In essence, both these talent shows for singers are very similar, with slight variations on a tried-and-tested format. (They are so similar, in fact, that "X Factor" was the subject of a lawsuit from Simon Fuller -- co-creator of the "Idol" concept. The suit was later settled and Fuller given a share of the "X Factor" rights.)
Crucially, though, "X Factor" has no age limit on contestants, while "American Idol" has an age limit of 28.
Both shows begin with auditions for the singers but instead of going head-to-head later in the series like Idol, "X Factor" places the singers in different categories that change from season to season. They have included: under 25, over 25, groups and solo artists, boys and girls.
Singers that make the grade are then sent on to a "boot camp" round (similar to Hollywood week in "Idol"). Another elimination takes place during boot camp: just 12 singers make it through to the final round, which, like "Idol," consists of live televised performances where viewers vote for their favorites.
In "X Factor," judges have more direct involvement with the artists by mentoring and coaching the 12 finalists. Everything from outfits, choreography and song choice in the final round goes through them.
This pits the judges against one another and sparks press coverage in the UK that tends to focus on this rivalry, faux or otherwise.
The female judges, which have included Sharon Osbourne in the past and currently features British popstar and footballer's wife Cheryl Cole (who has boosted the show's glamour quotient) are also subject to scrutiny for their outfits in the British press and also for supposed catfights and petty jealousies.
The two shows' moneymaking formula differs, too: "American Idol" makes its money through sponsorship and advertising, while "X Factor" also makes a lot of money from its viewers, mostly teens and tweens: millions of them phone in each week to vote for their favorite wannabe stars at the equivalent of 55 cents a call.
However "American Idol" arguably has a bigger pool of talent compared to "X Factor." It has certainly created bigger stars, generated more album sales and Grammy nominations and wins.
"American Idol," which is entering its ninth season this week, has been the United States' most popular television program for the past five years and has launched the careers of singers such as Fantasia, Kelly Clarkson, Carrie Underwood, Chris Daughtry and Jennifer Hudson.
The most notable winner of "X Factor" is Leona Lewis -- who has had the full weight of Cowell's clout thrown behind her in the United States.
She signed with Clive Davis' record label, performed on the Oprah show and was promptly catapulted to the top of the Billboard chart with her single, "Bleeding Love." Both her albums, "Spirit" and "Echo," have also topped the Billboard chart.
Other "X Factor" winners have not fared so well. In the aftermath of the show, they are immensely successful, with their debut singles more often than not landing the coveted British Christmas number one spot.
But their success soon wanes as the reality show machine pumps out another winner and the public turns their attention to them.
"X Factor" also tends to have a lot of novelty-value acts that in the past have included Chico, a cut-price Ricky Martin wannabe; and Jedward, the telegenic teenage twins who confounded some of the judges with their bad singing and dancing, yet still got voted back every week by the (largely female) viewing public.
However, the fact remains that no matter who wins the show, the biggest winner is Cowell. He created the show and owns most of its rights. All winners also release their album through Sony, the parent company of Syco, Cowell's entertainment firm.
Little wonder, then, that Cowell is keen to bring this particular cash cow to a bigger market in the United States.
Fox says it plans to premiere the U.S. version of "X Factor" in fall 2011 when "American Idol" is on hiatus. It remains to be seen whether it will be on a permanent break once "X Factor" launches Stateside.
Agnes Teh contributed to this article