Differences really lie in the applications of these forms, but more on that later. It makes little difference which style you pick when good health is the motivation for studying Tai Chi Ch'uan. All the styles advocate the health aspects to one degree or another. Some put stress more on relaxation then others, such as Chang Man Ching short form version. This style is referred to as small frame Tai Chi.
Small frame means the hand forms tend to be close to the body.
The arms are not extended as mush as you would see in so-called large frame styles. In the large frame styles the arms are extended further away from the body. There has to be a reason for this and there is. In the larger frame style there is more emphasis on the combat use of the movement, and in the small frame styles, less is seen of combat emphasis and more on softness and relaxation. Such differences depend on the intent of the creator when the style was developed.