Hello, these phones are very similar and there main difference is essentially size, apart from the fact that the 1520 has a few advantages...
1520
-has larger battery
-has larger 6in screen
-supports Glance feature
-has an IPS LCD display
-supports micro SD cards
-supports LTE in the U.S
930
-has a sharper AMOLED display
What I have listed under the 1520, the 930 doesn't have, and what I have listed under the 930, the 1520 doesn't have. These are really the only differences between these two phones.
They were made to pretty much be the same phone in two different sizes closely related, like the iPhone 6 & iPhone 6 plus...they both have the exact same camera..Lastly the 1520 is a few months older so its often found much cheaper