Mariah Carey at her peak had a greater voice than Beyonce on her best day. And she has better songs. Beyonce is talented but she doesn't have music that will be relevant later. No classic songs like "All I want for Christmas" or "Hero". She's more popular than her body of work.
Mariah Carey's vocal cords are messed up or something. She has some kind of health issue with the cords in her throat that allow her to sing notes that a normal human being isn't supposed to sing. She is in the Guinness Book of World Records for it. She has excellent songs. Her songs are very unique. She really does have her own style.
That said Beyonce to me is on another level. The level of artsy in her music is superb. I don't really listen to either of them in terms of their albums, but Beyonce's last album:
Was a masterpiece. Every song is unique and a part of who she is. The videos helped enhance the vision she wanted her viewers/listeners to see and hear. She put them through a view of her life. Of "Beyonce" (hence the album name). Her struggles (getting over the death of a friend), her love (Jay Z and Blue Ivy), her own thoughts (arrogance in Bow Down), and even powerful heartfelt messages (Pretty Hurts). She wanted people to feel what she feels.
I don't see how you can put Mariah on the same level as Bey.
Well to be honest I did use to be a big fan of Mariah amd her songs when I was growing up, but it's not like I knew about her when Ishe first came out or her original songs, and even no I'm not a big fan of hers once again.
As for Beyoncé who doesn't know if her? But besides that yes I love her music I grew up listening to her when she was a member of Destiny's Child and even when she went solo she just shined even more. I know just abut all of her songs and love all of them. But over all I've never been an obsessed fan of hers and I'm actually loosing beginnig to like her less and less as well because she doesn't even sing anymore now she just "tires to" rap and she's not very good at it.
But if I had to choose I think it's clear that Beyoncé wins this battle no doubt.