SquareTrade has drop-tested the new Samsung Galaxy S4 and found that it is more breakable than the iPhone 5 of Galaxy S3. Normally device manufacturers would want to increase durability with each revision, though this is sometimes hard to do. You can see video of their drop test below:
SquareTrade also put together this interesting infographic that compares the results of their various tests. They find that the Galaxy S4 is more breakable than the iPhone 5 or Galaxy S3.
The reason for the susceptibility to damage seems to be due to the large size. Not only is it harder to hold, it's also more fragile. Ty Shay of SquareTrade says, "Accidents are inevitable. We all know someone that has broken their phone. ... There is no denying the Samsung S4 is a terrific smartphone, but our results show it is not as forgiving as other devices to the clumsy among us."