Ok, so i was all set to choose the M&P 15 MOE, but THEN ...

My local dealer is having a one-day deal on the SIG 556 Classic with a rotary diopter.  I fell in love with this rifle by looking and holding it a few months back, but I read some bad reviews (primarily too heavy @ 1.5 lbs over the average AR-15 weight) and too overpriced (about $1400 with a rear diopter, $1600 with a SIG brand cheap-ass red dot optic.  Here it is:  Isn't she sweet?    What a great deal.  Now I'm a little conflicted. At full retail, it's a no-brainer -- I'd go with the M&P.  But at this price, the SIG is such a great bargain, I might have to reconsider.  Thoughts?