Eyebrows:
If you look here, Britney in Piece of Me is more like a "Round Natural"
whereas here, she has more like a "Seductive Natural"
or not? Guys I don't know. But it's DEFINITELY something with the eye - eyebrow makeup.
Now she looks like a mom-singer, gimme more pic is like a singer singer.
I don't know if it makes sense but... yeah.
UPDATE:
Here are some pics that I edited to see the difference:
Pic 1:
Pic 2:
Pic 3:
Pic 4 & Pic 5: http://britney-galaxy.com/universe/topic/10829-i-think-this-is-why-britney-doesnt-have-a-fierce-look-on-pom-makeup/?p=227132