Most everyone outside of poser-verse models human figures with their arms at a (more natural) 45 degree angle, as it allows for better rigging and more natural motion.

If you were to go to school for computer animation, you would be modeling your humanoid figures with arms bent at 45 degrees. 

10 years ago the classic T-pose was much more common. Today, poser is pretty much the only area that uses T-pose modeling. It's not a natural pose and puts too much emphasis on muscle definition that is not apparent without the flexing that is required to hold a T-pose. This is why "the industry" has steered away from T-pose modeling. 

 

~Shane