This bike is designed for hauling. The Yuba Spicy Curry has a combined capacity of 500lbs (200lbs on the front including rider, and 300lbs of passengers or cargo on the back). To help move this weight, you’d expect a decent motor, and the Bosch Performance Line CX delivers. Normally only found on mountain bikes, the 75Nm of torque makes light work of hills, even with the heavy load.
E-bikes mostly use motors and battery options from a few major suppliers: Bosch, Yamaha, Shimano, and Brose. A few other brands exist, but are less reliable or powerful. Some, like the Yamaha system, have more torque and others are quieter. But generally all four make good options. Look for motor output (in watts) which will give you an idea of total power. But watt hours (Wh) is perhaps a better figure to use—it takes into account battery output and life to give a truer reflection of power.