i'm suprised you guys are all bashing My Baby . It's genuinely one of my favourite songs on Circus. That very last high note at the end is epic.
I *****d My Baby so much I think my family thought I was insane when they caught me blasting that song one day. ....the ending of that song is so beautiful.
Womanizer = Gimme More
Circus > Piece Of Me
Out From Under < Radar
Kill The Lights > Break The Ice (I actually hated that "Break The Ice" was a single -- such a poor choice)
Shattered Glass > Heaven On Earth
If U Seek Amy = Get Naked
Unusual You = Freakshow ("Unusual You" is fantastic, but "Freakshow" was ahead of its time)
Blur < Toy Soldier
Mmm Papi < Hot As Ice
Mannequin < Ooh Ooh Baby
Lace And Leather < Perfect Lover
My Baby < Why Should I Be Sad
(Pretty similar to IfUSeekLEM's)
Overall, I've listened to the Circus tracks more (2319 times) than Blackout's (2106 times). As a whole, Blackout is better, but if the Circus bonus tracks had replaced some of the last 5 tracks on Circus, I'd be singing a different tune. Why "Phonography" was a bonus track is something I'll never get over.
Womanizer = Gimme More
Circus < Piece Of Me
Out From Under < Radar
Kill The Lights > Break The Ice
Shattered Glass < Heaven On Earth
If U Seek Amy > Get Naked
Unusual You > Freakshow
Blur < Toy Soldier
Mmm Papi < Hot As Ice
Mannequin < Ooh Ooh Baby
Lace And Leather < Perfect Lover
My Baby < Why Should I Be Sad
BETTER
They're both fabulous productions, but I'll say this: "Circus" is a better performance song, while "Piece Of Me" is better for the club.
When it came to comparing them, it kinda' came down to my play counts (can you tell that I'm obsessed with my play counts?) and "Circus" has about 90 more than "Piece Of Me."
And I love breakin' it down to "Circus" over "Piece Of Me."
The true tea right there.
. It's genuinely one of my favourite songs on Circus. That very last high note at the end is epic.
I think my family thought I was insane when they caught me blasting that song one day. 
....the ending of that song is so beautiful. 
