According to the Guardian:
The [Samsung Galaxy] S6 is 6.8mm thick and weighs 138g, which makes it thinner but heavier than Apple’s 6.9mm thick, 132g iPhone 6 and thinner than most other top-end smartphones, including the 7mm thick S6 Edge.
Which are you going to go for? Are you going to save yourself a tenth of a millimetre—100µm—or six grams? At least you could measure six grams with ordinary kitchen scales, even though you wouldn’t be able to feel the difference. You’d need a micrometer to measure 100µm, and how many people have one of those at home?