^^^ whitney has a more pleasent and commercial voice than mariah ...... and her low notes are stronger ........ Mariah lows are weak...sometimes mariah starts whispering and its really annoying,even her choir is lauder than her ....
also mariah may go higher but not everybody likes that because you dont even know the pitch of her voice when she does her whistle register
both are amazing voices but WHITNEY IS WHITNEY
anyways i found this
As of May 2006, Houston is executive producing The Cheetah Girls sequel The Cheetah Girls 2: When In Spain. Whitney Houston is also recording a new album although there has been little press interest surrounding the project. In an issue of XXL's Hip-Hop Soul Bryan Michael Cox said that they were "making great music. Whitney's going to be a surprise", and predicted a career comeback for Houston on the scale of those staged by Mariah Carey and Mary J. Blige. The album has been in production for over two years and is rumored to feature contributions from Jermaine Dupri, Lil Jon, Babyface, Pharrell Williams, Rodney Jerkins, and Missy Elliott. In 2004 Houston received a trophy at the Womens World Awards in Europe, and she performed live at the 2006 Winter Olympics in Torino, Italy. Subsequent news outlets reported that Houston is again fighting drug addiction. The National Enquirer published pictures of a bathroom (purportedly Houston's) littered with drug paraphernalia, and credited the pictures to Tina Brown (Bobby Brown's sister). Tina Brown also said that there were holes drilled in the walls of her apartment so Houston could see if anyone was entering. The story has received substantial coverage in the media, and in April 2006 it was rumored that Houston had returned to drug rehabilitation for the third time, but in an interview with S2S Magazine Houston's friend (singer Cherelle) denied the story. Cherelle stated that Houston has been rehabilitated for a long time now. It has also been reported that Houston was suffering from a brain tumour; however, Houston's website issued the following statement: "Please note that reports on Whitney's health circulating in the media at present are not true and totally unfounded."
In August 2006, it was reported that Osama bin Laden was apparently "obsessed” with the pop diva. Bin Laden, according to novelist Kola Boof who claims to have been the terrorist mastermind’s "sex slave,” considered Houston to be "the most beautiful woman he’d ever seen,” and even talked about having her husband (Brown) killed so he could make Houston one of his wives.
"He [Bin Laden] said he wanted to give [her] a mansion that he owned in a suburb of Khartoum,” Boof told reporters. "He explained to me that to possess Whitney he would be willing to break his color rule and make her one of his wives.” Bin Laden is apparently "dismissive of black women,” but was taken by Houston’s beauty, even reportedly carried photographs of the singer in his briefcase.
August 31,2006 Whitney announced that she will be releasing her album by the end of this year. "I'm letting all these other women release their album so that i can have my time to shine" she announced. She also revealed the names of 3 tracks of her album "Turn me up" "Drop it" and a ballad titled "A woman's heart". Whitney was quoted saying "I havent been able to showcase my voice as much as i have in this record, but i also left a few songs out there for those of you who love the club". Rumor has it she will also be doing a duet with Pop-star Christina Aguilera.
... all you have to do is listen to "butterfly" and listen how her choir is lauder than her 
Mariah has crazy range, i give her that, but do you not hear the power and tone of whitney's voice? mariah shines in her clips when she hits the whistle register.........outside of that she is an average singer ........ i would love to see mariah sing "I will always love you" in that same key