The Ui6 is the same frame, components, tires, brakes, as the Ui5, but it comes with a 500 watt motor (instead of the Ui5's 350 watt), and a 48 Volt, 13 AH Samsung battery. It also has a newer display from Magnum. It's priced (MSRP $1799) at only $100 more than the previous Ui5, so its a pretty good value. The motor has a peak output of 700 watts.
Vs, The Metro is a different ebike , priced at $1999. It has the same wattage motor, but its Das-Kit versus Bafang, and the ebike is capable of a higher speed at 28 mph (assist only). (versus 22 mph for Ui6). The display is different too, a bit nicer and larger. It'll have a slightly higher grade derailleur (Shimano Altus), and better trigger shifter. And hydraulic brakes vs mechanical brakes on Ui6. Also has a better quality suspension fork than the Ui6. Lastly, they are including a suspension seat post. Functional but won't be the higher quality of a Thud Buster or Body Float.