I used to believe that the color of the sabot was an indication of the diameter of the bullet it would accept. Then I started seeing different colored sabots that would shoot the same diameter. The black sabot in my experience usually indicated a high pressure .451-.452 diameter sabot. The green sabots are .429-.430. The orange sabots are .457-.458 diameter for the .50 caliber rifles. This might vary from sabot maker to maker.

As for loading ease I think you find the make of the sabot a lot more important. Each sabot maker like Harvester and MMP have a different thickness in the petals of the sabot. This is why some of them even tho the same color, will load so different.