The Dewalt DW718 and DWS780 are Sliding compound miter saws with 12" blades.
The saws appear essentially identical but there are many minor differences.
The DWS780 is 3800rpm vs 3600rpm for the DW718 both motors are 15Amps.
The DWS780 has a much improved dust collection tube. You can see the larger opening of the dust collection tube easily from almost any photo.
The blade safety fence of the DWS780 is improved to allow slightly bigger cuts. Vertical capacity of baseboard against the fence is up to 6-3/4" from 6-1/2", Vertical capacity of Crown Molding vertically nested us up to 7-1/2" from 6-5/8", and Horizontal Capacity Crown Moulding laying flat is up to 13-3/4" from 11-1/4" for the DW718.
The DWS780 weighs in 3 lbs heavier at 56 lbs from 53 lbs for the DW718.
Additionally the XPS light is Standard Equipment on the DWS780. Optional and additional on the DW718.
Clearly the best ever DW718 has been improved on, The DWS780 is a clear winner and the newest best saw ever.