Disclaimer: I am a 1520 user for 16 months. I am biased. I chose 1520 over 930.
Let's look at the tale of the tape, shall we?
Nokia Lumia 1520 vs. Nokia Lumia 930 - GSMArena.com
These 2 devices are the same in a lot of respects:
Data speed
SoC
RAM
Internal storage
Camera
Sensors
WiFi
Bluetooth
Wireless charging
That said, avoid the AT&T RM-940 variant. Internal storage is cut in half and the Qi is stripped out for PMA with a required add on case.
930 has arguably a better screen. Personally I don't like AMOLED as much (which 930 has) and the 441 ppi is a bit of overkill, IMHO. 930 is more pocketable. No arguments there. 930 has Gorilla Glass 3 vs the Gorilla Glass 2 on 1520.
If you like a larger phone, the 1520 has a full hd IPS LCD with 367 ppi that looks gorgeous and is very readable in direct sunlight. LOVE that about my Beast Phone[SUP]TM[/SUP]
With the 1520 you gain Glance. You get an SD card slot: great for consumable media, extended photo shoots and just plain keeping more stuff on your phone. The battery endurance on the 1520 is phenomenal. All reports of the 930 is that it is average or below on battery.
My money went to 1520.
One caveat. If you can buy from a trusted source to help ensure you get a phone that was not abused or pumped through too many recharge cycles it would be wise as some of these units were built 2 years ago now. You could replace the battery if you are comfortable opening a sealed device.