The difference between NBW-A and NBW-C:
First:
Skin Analyser(NBW-C) can test wrinkles and the freckles,it has 5 main function:
1)test of skin moisture, skin oil content
2)test of skin elasticity
3)test of  pigment(freckles)
4)test of  hair pore
5) test of skin smoothness(wrinkles)
Skin Analyser System (NBW-A) is mainly for the test of freckle and wrinkle

Second:
Skin Analyser(NBW-C) can have the accurate test data.
Skin Analyser System (NBW-A) can not have the accurate test data.

Third:
Skin Analyser(NBW-C) is for the whole body and face.
Skin Analyser System (NBW-A) is only for the face.
Now the most popular one is NBW-C,also it is the most professional one.