Is the barrel too short on the 239 to get the performance out of .357 sig?

I like the size of the 239 for carry.

It depends on what you're looking for.  It probably will do 1350 with a 125gr bullet, which is a good bit better then 9mm from the same barrel.  You can look at ballistics by the inch and compare it to other rounds.

http://www.ballisticsbytheinch.com/calibers.html

I've been carrying the 239 SAS gen 2 (357) for several years as an off duty and backup.
I've had no issues with the 357 Sig round.
And yes, it's a great carry gun with a proper holster since it's a heavy gun.

I wonder what weighs more a glock 19 with 15+1 1 or the 239?

my guess the 239 weighs a little more.

My go to daily wear is a glock 19 in a supertuck so I am guessing that style should work well with the sig.

The more I read about .357 sig the more i like it. I am almost of the opinion that gel testing sets a baseline and bullet manufactures are developing rounds for the test.

It seems to me the extra couple hundred fps from the .357 sig make it far more effective after going through clothes belts cell phones car doors glass etc than a 9mm.

Not sure about the weight difference between the two but I like an all steel gun over tactical Tupperware.  
I use a Crossbreed IWB holster and a solid leather ankle holster.
I'm a big fan of the 357.

I currently have a p229 in 357sig. The barrel length should not make a difference at self defense ranges of fifty yards or closer when fired from a p239. Barrel length difference of about a quarter inch has little effect on power. What effects performance is shot placement in most cases.

The company I work for at one time had to do ballistics performance on a bulletproofing material. Being the resident gun nut......err.......expert, I was tapped to do the shooting. With 9mm to 45acp in handguns which included the 357 sig. Ballistic jell penetration showed little difference when barrel length was looked at in close quarters battle house distance was used.

In real world use by me on the family ranch, the 357sig brought down a doe and coyote at thirty yards. Again shot placement played a major factor in how the round performed.

In short, I would not worry about the short barrel in a p239 when in a defense situation.