Both collections could've been better. Madonna's emits the likes of Vogue, Into The Groove, Justify My Love, Crazy For You, Gambler, Who's That Girl?, Causing A Commotion, American Pie, The Look Of Love, Hanky Panky, Rescue Me, I'll Remember, This Used To Be My Playground, You'll See, You Must Love Me, Don't Cry For Me Argentina, Another Suitcase in Another Hall, Beautiful Stranger (A grand total of 18 UK Top 10 hits, including 5 #1s!

)
Mariah's emits Someday, I Don't Wanna Cry, All I Want For Christmas Is You, Open Arms, Breakdown, Sweetheart, Crybaby, Loverboy, Never Too Far, Through The Rain, Boy (I Need You), I Know What You Want, We Belong Together, It's Like That, Get Your Number, Don't Forget About Us, Say Somethin', Touch My Body, My Love, Bye Bye, Obsessed, I'll Be Lovin' U Long Time, I Stay In Love, I Want To Know What Love Is, Oh Santa!, H.A.T.E.U. (9 U.K. Top 10 hits)
I would prefer Madonna's if it was given as a gift, but I'd never buy collections that are so wrecklessly put together. Therefore:
neither!