Actually, according the their respective websites, the HK is actually SMALLER than the Sig.
From
http://www.hecklerkoch-usa.com/
Specifications
9mm .357 SIG .40 S&W .45 ACP
Magazine Capacity *13 *12 *12 8
Sights 3-dot 3-dot 3-dot 3-dot
Width 1.14 in. 1.14 in. 1.14 in. 1.14 in.
Height 5.00 in. 5.00 in. 5.00 in. 5.06 in.
Sight Radius 5.35 in. 5.35 in. 5.35 in. 5.63 in.
Weight 1.47 lb 1.53 lb 1.53 lb 1.60 lb
Barrel Length 3.58 in. 3.58 in. 3.58 in. 3.80 in.
*US Civilian magazine capacity is 10 rounds.
From
http://www.remtek.com/arms/sig/model/239/239.htm
SIG SAUER P239
Specifications Operation Semiautomatic, mechanically
locked, recoil operated
Trigger Double-action/single-action
or double-action only
Safety Patented automatic firing-pin lock
Caliber 9mm Luger .357 SIG .40 S&W
Length, overall 6.6" 6.6" 6.6"
Height, overall 5.1" 5.1" 5.1"
Width, overall 1.2" 1.2" 1.2"
Barrel length 3.6" 3.6" 3.6"
Rifling twist 1 in 10" 1 in 16" 1 in 15""
Rifling grooves 6 6 6
Sight radius 5.2" 5.2" 5.2"
Weight, w/o
magazine 25.2 oz. 25.2 oz. 25.2 oz.
Weight,
empty magazine 2.3 oz. 2.3 oz. 2.3 oz.
Trigger pull DA 9.5 lbs.,
SA 4 lbs. DA 9.5 lbs.,
SA 4 lbs. DA 9.5 lbs.,
SA 4 lbs.
Magazine capacity 8 rounds 7 rounds 7 rounds
Now I personally feel that the Sig gives the illusion and feel of a smaller flatter gun, but the numbers are there. I have yet to go and measure the two side by side, but I am also trying to decide between the two. The Sig is a little more comfortable and the HK holds more rounds.