It really is a simple e-bike, and while I could go on about the frame (aluminium), and the weight (very light), the experience of using this bike for a few days is more interesting. While it feels like a less high-tech product than others in this list (no gears; a shorter battery life of 30 miles; two modes not three), it basically retails at half the price as those competitors – and I certainly didn't find it to be half as good.
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.