I currently have the M&P 15OR Optic Ready that I bought 3 years ago and wanna know the difference in these 2 models. My buddy was looking at the M&P Sport II and wants to buy it, but we both wanna know what the difference is? Why is the M&P 15OR model $2-300 more than the Sport II?? I've tried researching but really can't pin-point the reasons for the price differences and what's better etc. Any info you can provide me will be greatly appreciated. Thanks