The Moto X4 is now $399. $300 off the $699 release price last year. Since then it's been available for $599 and $499. A well received phone but at $699 it was way too pricey for a mid range phone.
Black Sold Out or Sterling Blue colours.
Overall similar specs (same storage, RAM & snapdragon 630 processor) to the G6 Plus but the X4 screen is a bit smaller 5.2" vs 5.9". However the X4 camera looks better on paper (Dual 12mp/8mp f2.0 & f2.2 vs dual 12mp/5mp f/1.8 on the rear and 16mp front camera vs 8mp front camera). Note that X4 is upgradable to Android Oreo 8.1, G6 Plus has it out of the box.