Front view of bodies

Top is old body while the bottom one is the Pure Skin body.

Quick shot of the heads

Note that there is a slight skin colour difference. This is not because of the lightning or flash. The old body is paler and bit yellow while the PS body has a lovely peachy glow to it which looks much healthier ^^;;

Sitting up

The old body's legs has a slight tendency to float up and the torso to lean back. The PS body sits up beautifully and is seriously stable.

Sitting up #02

From the side its really noticeable how much the old body leans backwards while the PS body sits naturally with a straight back and legs on ground.

The Yuni pose XD

The old body can do it with legs further apart and have a hard time balancing. In order to keep the pose she either has to lean forward or have her hands supporting her. Also note that this body is tightly strung and wired which is one of the factors to why she can do this pose.

The Yuni pose again...

The PS body does it with legs together and is quite stable. Keep in mind that this body at the moment is loosely strung and had it been strung better, the pose would have been better. 

Hip joint #01

The old body joint is and awkward jutting out 'ball' which makes it difficult to sit.

Hip joint #02

The smooth rounded 'ball' of the PS body makes it so much easier to sit and stand by filling the grooves on the lower torso and so stabilizing the body better.

Front view of hips & elbow joints

For the elbow 'ball' at the old body is less rounded and the opening is shorter than the PS body. This limits the hand poses of the old body as when the elastic meets the end of the "U" while bending the arm, it sends the arm back to where it is. Hard to explain X_x;

The opening "U" shape where the legs meets the body where the string goes through for the old body is 'shorter' while the PS body has a longer opening. This helps for sitting the body as the elastic has more leeway to more forward. This helps awfully a lot when sitting and has eliminated the lean backward tendency of old body Minis. Of course unnoticeable is the snaps where the hip joint is that also helps in making the PS body more stable.

Back view

Not much changes ne ? XD
Unnoticeable in the picture is the hidden 'lever' thing in the old msd body at the waist joint that keeps the upper torso from leaning backwards or forwards too much. This 'lever' is present in the PS body but in a much shrunken size allowing the torso more movement forwards or backwards.

Also the openings where the hand meets the shoulder are widened on the PS body compared to the old body, allowing the PS body to hold her poses better when the arm is raised or etc.

Back of knees

Quite a big improvement on the knee joint. The old body is on the left where the 'ball' is rounder, half covered by the upper thigh and the "U" opening isn't quite as long as the one on the PS body. The 'ball' on the PS body is molded right into the calf but on the old body, it has to be glued onto the calf.

The thighs on the PS body are a tad slimmer and less rounded than the old body ones giving it a less 'bulky' shape.

Ankle

The old body's ankle joint 'ball' is glued on to the calf and the opening for the elastic to pass through is at the bottom part where it joins to the foot. On the PS body however, the joint 'ball' is free and the openings are at the top. This system allows for the S-hook that holds the foot to the elastic to rest on the 'bowl-like' area of the 'ball' joint for easy swapping of feet XD

Side view of legs

In the old body, the joints do not 'fit' together as well as the PS body one does as can been seen in the thigh to calf joint. Also the PS body legs has a more natural look to it as there is no jutting out ball from the back of the ankle. I wonder why they did not do the same thing for the arm elbow 'ball' joints though.

Knees up

While both can raise up one knee when lying down, the old body does it with difficulty while on the PS, the pose just snaps into place. Also the PS body holds this pose in a more natural position and does not show so much of the 'tunnel' inside the thigh.

Knees up side view

To illustrate what I meant. The body in front is the old body while the one at the back is the PS body. The longer "U" of the knee 'ball' joint mentioned earlier helped in keeping the bend part more upright and with a less tendency to kick back. This however does not happen with the old body ^^;;