Your post reminds me of the year when I heard these two songs played again and again on radio. I had a long drive to work that year, I heard them so many times and they are so interestingly different, such that 1) one song will immediately remind me the other; 2) I was tired of both at that time, and 3) I compared them at that time.
I can't say I like Macy Gray's voice -- I admir her for that fact that she even tried to be a singer with that voice, but I felt real when I heard "I try to say goodbye and I choke, I try to walk away and I stumble";
I love Iglesias' voice, but I felt vain when I heard "I can be your hero baby".
It's all personal thought.