LG G3 is a big brother of LG G2 because maximum things are same but there are some important feature are givien below
There are 5.5 QHD true ips 534 ppi screen with gorilla glass 3 and it has qualcomn snapdraon 801 chipset with quad core 2.5 GHz karit 400 processor it has 3 gb ram.
There are 13 mp rear camera and 2.1 mp front camera and comes in 16gb and 32 gb of built storage expandable via a micro sd card. It has also 3, 000mAh user replaceable battery.
The bad things about this phone is that I has not a microUSB 3.0 port and this is not water and dust resistance.
In my opinion you should by this phone and try it the performance of this phone is very good.