In a friction drive motor, a small, solid wheel rotates against the side of the tire in order to drive it. The first motorcycles used the same concept, with a motor mounted above the front wheel. The problem is that the drive rubs at the side of the tire. It's inefficient, and it quickly wears the sidewall away. Tires need to be replaced every couple hundred miles. For this reason, you'll seldom see electric bikes with this type of drive anymore.
ELECTRONIC CONTROL  The Zero-Smart-Start speed controller delivers ease of use and smooth drive control and offers a multi-function variable speed output.  It is state of the art, producing consistent efficient power.  The automatic Pedal Assist mode produces a power burst that dramatically assists the pedaling effort.  The Zero-Smart-Start electronic throttle control allows the rider to relax and not pedal at all. 

“Even if you deal with the tubing supply chain and consumer retail price tolerance, there is no supply chain here for the cables, shifters, crank sets, chains, saddles, and every other part. It would take decades to set all of this up, but you would first have to get consumers to the point where they will pay $1,800 for the bike that they could get for $400.”
Though aside from the extra battery and abundance of included accessories, Riese and Muller’s use of a Gate’s belt drive means no shifting of gears, no greasy maintenance, and much higher durability. If you have the money to spend, Riese and Muller’s Delite nuvinci is one of the best on the market and an ebike we just couldn’t get enough of during our own tests.
Because e-bikes are capable of greater speeds for longer periods of time than standard bikes, you want extra control. Wider tires provide traction and some bump absorption with little penalty. You also want strong brakes to slow you (and all that extra weight) easily. It's worth looking at the quality of the brakes and investing in bikes with better ones if you can.