Power Consumption
The Ryzen 7 1700X's lower clock speed means that it takes a reasonable chop out of the R7 1800X's power consumption.
That same advice is applicable to the R7 1700, whose 65W TDP translates into lower multi-thread power consumption than a four-core Core i7-7700K, and you already know that it obliterates said chip in applications such as Cinebench and HandBrake.
AMD has done an impressive job in the performance-per-watt metric on Ryzen, with this design philosophy best exemplified by the R7 1700.
