I recently bought a Bustmaster M4 ORC (Optics Ready Carbine [flat-top, no sights]) for a great price (700). If you are planning on adding an Eotech anyways, that might be the way to go. However, as has been said the new S/W weapon comes with the flat-top, BUIS, and railed front end, however, I'm not sure of the cost on those. On the Bushmaster I started with the base price of $700, added the flip up BUIS for another $80, and a Knights RAIS for another $60, so for $840 I got a pretty sweet setup. So compare that with the S/W and go from there. I don't have any operational or range experience with the S/W, but I have used the BM and FN M4s on range and field.
drew