Over the years, I have built a number of stands for reproduction and antique armors. I keep changing the design as time goes on.
I don't know that one is really better than another, but they are different.
Sometimes I change the stand to make it easier/faster to build, sometimes in an effort to make it display the specific piece better.
In general, I am trying to build a stable stand that will stand on its own without a base and which will hold the armor in a
reasonably accurate static position. This means that I tend to include some basic features. These include:
The legs splay out some. They aren't vertical. This adds to the stability of the stand, and makes the armor look more natural.
The feet angle out. Again, this makes the stand more stable and looks more like a person standing.
The legs have a profile that reflects the thigh, knee and calf. This helps to hold the armour in the right position.
The body has a profile that reflects the shoulders, chest, waist and hips. This helps the look of the display and also allows me to support more of the armour, limiting stress on the pieces.
The shoulders (usually) have some slope to properly mimic the human body. This helps to properly display the breastplate/cuirass, gorget and shoulders.
I have a hard time with arms. Sometimes I can just let them dangle, other times I need a little more structure so I have added some upper arm. I often give up and use a mechanism that I found on a stand that I obtained with a part armor. If you run a wire or cable inside the arm and secure it to the shoulder of the stand or a relevant bit of the shoulder armor and then hook it to the wrist of the vambrace or cuff of the gauntlet, you can provide a bend to the arm. This only works is the arm is reasonably solid - an articulated arm with pauldron works well. It won't work with separate parts.
You will notice that the waist on these stands is pretty narrow. It will look very unnatural. That is because the sides are not at the center of the body. The waist has to be cut in to reflect the shape of the body at the point that aligns with the center of the femur.