PI is indeed more shiny and gloosy. Colour is brigther. HT is a bit darker with very-very soft purple tone.
About the soft material in the arm, this one is annoying, this rubber prevent the arm to fold maximum. I have to hold it if I want to fold it completely. And still not as deep as PI arm can go. PI arm hinge is consist of two hinge points. This design makes it more poseable, and very stable/firm.
But PI neck is annoying, head movement is limited, cannot look up/above. Thigh articulation is better than HT. HT fingers, knee and ankle articulation is better.
PI is a bit overprice.
But after you hold the figure in your hand and feel the weight and feeling of the material, the colour and glossy paint, the shape. You will feel a very big temptation to have it. So heavy that you can say this is "iron" man.