you will have to forgive me three outputs. Now explain why that is preferable?
Sorry i'm a novice trying to learn 
3 outputs mean that if you're connecting an amp and sub, there headunit has dedicated outputs on the back, one for the front speakers, one for the rear speakers and one for the subwoofer, usually meaning that adjusting speakers is much easier as most can be done from the headunit itself.
Very handy for the sub as you can easily up the bass on the go without having to adjust the amp.
