Advantages and disadvantages of skeletal animation against sprite sheet animations

In the Unity 4.3 there is an option to animate different parts of a character body using the dope sheets, so what option should i prefer, this one or the animation through the sprite sheets and why?

It really depends on your game, but it’s basically a CPU vs Memory trade off. Animating an object using multiple pieces will generally be a lot less memory than sprite sheets, but will require more CPU/GPU to render. Sprite sheets are as simple as it gets, but they can quickly consume a ton of memory, especially if you are trying to animate at 30fps and/or at high resolutions. Most games use a mix of techniques, depending on the kind of thing being animated.

It it also a matter of flexibility. If you know in advance exactly how you want your character is to move, and they will only move in that manner (jump, run, punch) a sprite sheet it great. If you want the animation to be dynamic. Something that can be changed on the fly, bones would be better. Either way the believability of the movement is going to be based on the quality of the animation/animator. And like Makecodenow said you don’t have to only use one or the other, you can mix and match to fit your needs. The more tools you have the better.