can you tell me their difference in terms of note?

here is a video of whitney houston and charice pempengco of one moment
in time. i like to ask why does charice sound more high pitched when
she's hitting high notes, does this mean that she doesn't hit the note
well or is she screaming?whereas whitney sounds more full..which of
the following hit the higher note in the part of high notes? thanks...

here's whitney:

http://www.youtube.com/watch?v=BxlEHuP3LMMfeature=related

charice:

http://www.youtube.com/watch?v=vnyIVvHY7KQ