The electric mountain bikes are going to provide more suspension cushioning and be 10 lbs lighter than the average "commuter" bike. The same suspension that is designed for rough trails helps with bad roads in the city. Commuter type bikes tend to be much heavier in terms fo the frames and the wheels and the tires which is not a problem when riding on relatively flat ground but is a problem for hauling the bike up flights of stairs.
If traffic is only going to allow for speeds of 10-15 mph on city streets then a regular bicycle may be equally useful and it will be 30 lbs lighter. A folding bike like the Dahon folding bikes sell for $800 and weigh less than 30 lbs and come with a rear rack and front and rear wheel fenders.