difference in aero bar design
First, one small point. The two pictures show different types of extensions, not bars. Bars are still what the extensions attach to (Commonly called either aerobars or bullhorns). 

Extensions come in various types, including (but not necessarily limited to) S bend, F bend, straight, skip tip. Each have their advantages and disadvantages. Most wind tunnel tests have shown that the hands angled slightly down so the line is straight along the tops of the wrist arms is faster. However, this may not be comfortable for some people depending on distance and position.

Of just as much if not more important is the shape of the base bar, and the extensions/pad system being used. The entire aerobar/extension setup (Commonly referred to as the cockpit) is also highly dependent on rider position, and often the canard used in the TT/triathlon world is that you almost determine your cockpit first, and then your frame.

For the second point, the photo being shown of Matt Goss is a bike that is set up according to UCI rules. These are very stringent, and regulate such things as the angle of the forearms according to the ground, the position of the seat front to back in relation to the BB, etc. If you remember the Levi Leipheimer praying mantis position, that would now be illegal according to UCI rules. They also dictate the shape of the aerobars and other factors (Such as a water bottle cage mounted between the arms. Wind tunnel tests have shown this is one of the best options, but is illegal according to UCI rules).

Caveat- One of the last Tours that Levi did, his bike was set up according to UCI rules, but he had it at the limits and was still able to approximate his praying mantis position. I remember Liggett commenting on it at the time.

However, unless you are competing in a specific National level time trial or higher where UCI rules apply, you can safely ignore the UCI guidelines.

As it is a huge impact both in comfort and performance, I highly suggest you get with an experienced fitter. Time trial/triathlon frames and setups are vastly different, as are the measurements and frame designations. (A 54cm is not necessarily a 54 cm, etc.)