Usher or Justin Timberlake?
 

Very hard one, but I think JT just edges it for me.

Usher

JT has been unbearable for a while now

Usher!

JT is so overrated, he has one good song

Neither

The one that rihleased this masterpiece

I want to say JT because FutureSex was a brilliant album (and Usher has no brilliant albums) but he's so bad lately.

On the balance of it, naming their greats...
Usher - DJ Got Us Fallin' in Love, Pop Ya Collar, Climax, Scream, Yeah, U Remind Me, Caught Up, Don't Look Down
JT - Signs, Sexyback, My Love, Lovestoned, What Goes Around, Senorita, Like I Love You, Cry me a River, Mirrors, Where is the Love, Bye Bye Bye

On numbers, JT wins I guess. So much more annoying and smug, though.

I always found Usher to be the smug one... but I haven't followed either of them for years so I am basing my choice on a decade or more back.

That being said... usher inflicted Bieber on the world... so I had to go JT

Yeah! > Timberlake's career