Which is the best smartphone for title "World's Slimmest"?

Today I searched for "Word Slimmest Smartphone" and found two different answers.

1. Gionee’s Elife S5.5 as "Slimmest smartphone 2014"

2. Sony Launches Xperia T3, 'World's Slimmest'

Its hard to believe which one is best and true. I want to buy a thinnest smartphone.

how to choose the right smartphone?