What sportsgeek said
There can also be some variation in your stance forward or backward that effects the muscles worked. If the weight is more forwad, like in a squat with the barbell in front of the head, you will work more quad than the traditional barbell on shoulders behind the head squat.
A wider stance like you say you have
should work your glutes more.
Personally, I get most soreness in the glutes and hips after squats, which I blame on my sitting on my ass in front of a computer so much for work.