Jeep lists the GVWR of the JKU at 5500 lbs. and curb weight at 4231 lbs. AEV lists the curb weight of the DC350 at 5400lbs. What I think you're also failing to take into account is what you have on the DC350;
61" X 60" Cored Composite Bed
Stamped Steel Cab Closeout
Double Cab Hardtop
Double Cab Rocker Guards
AEV Double Cab Rear Bumper
AEV Water Pump Kit
AEV Under Mount Tire Carrier
AEV 3.5" DualSport SC Suspension
AEV ProCal
AEV Jack Base
AEV Badging
AEV Instrument Cluster
AEV Logo Headrest
AEV Serialized Build Plaque
AEV Premium Front Bumper
IPF 901 Off-Road Lights
AEV Front Skid Plate
AEV Winch Mount
Warn 9.5cti Winch
AEV Heat Reduction Hood
AEV 17" Alloy Wheels
BFGoodrich 35" Mud-Terrain Tires.
Straight from AEV's FAQ on the Double Cab "The Brute Double Cab is not designed to be a replacement for a traditional pickup truck. The Brute Double Cab is designed for overland travel. The Brute Double Cab utilizes the factory trailer hitch, therefore retaining the Jeep Wrangler's 3,500lb max towing capacity. Since there is no standardized test for determining payload capacity, we recommend following Chrysler's suggested payload capacity of 892-1,000lbs (weight varies depending on trim level)."
From Motortrend, "Instead of a steel pickup box like the original Brute's, the new Double Cab uses a composite bed that weighs 140 pounds less than the steel bed, allowing the new Brute to tip the scales at about the same weight as a stock Wrangler Unlimited. Curb Weight 5200 lbs." Which was with the 6.4L Hemi, Dynatrac Pro Rock front and rear axles, and 37" tires.
According to Barton Jeep, "GVWR: 2,585kg (5,700lbs). Curb weight: 2,057kg (4,535lbs)"
http://www.bartonjeep.net/new/Jeep/2015-Jeep-Wrangler+Unlimited-abfb6f340a0a00021721b167693a814c.htm
Might be handy to look at the manufacturer for the source of the GVWR instead of just one site.