If you observe people doing the squat in an athletic facility or in a fitness club, you will most likely see them doing a sumo squat. This means that in your initial stance you assume a position with your feet wide apart and then squatting.
The sumo squat became ‘the squat’ in powerlifting and for good reason. You decrease the distance over which you must lift the weight and you can lift more weight. Rather than relying on mainly the quadriceps, glutes and hamstrings as in the squat with the legs hip or shoulder distance apart, the sumo squat also requires strength from the adductors.
Understand that any time there is a change in exercise execution, there is a corresponding change in the muscle involvement. Thus in the sumo squat there is a greater balance between all the muscles involved. In the hip-width-apart stance there is greater emphasis on the quadriceps, gluteus maximus and hamstrings, if the squat goes to thigh level while maintaining an arch in the lower back.
Keep in mind that the arch in the lower back plays an important role not only in muscular involvement, but also in safety. It is a must regardless of yourl stance.
To decide which type of squat is best suited for athletes you should look at what which muscles are being trained and how the squat relates specifically to sports movements, i.e. skill technique specificity. For example, athletes must be able to jump and run in most sports. In execution of these skills the legs are directly under the hips.
Thus your choice of squat is really quite simple. If you want to improve running and jumping ability, then you should do the hip-width- apart squat. If you are a weightlifter or power lifter, then the sumo squat may be more advantageous.
The main advantage of the sumo squat is in being able to lift more weight. But this should not be the top priority for athletes. Strength gains should be directed to improving skill execution and performance on the field, not to be stronger for the sake of being stronger.
For more information see Biomechanics and Kinesiology of Exercise.