The motor type could make a difference though. The Cambridge 200 watt motor is brushless, doubtless a Hall effect motor, while the Windsor/Salisbury have 180 watt brush motors. Hall effect motors tend to give better torque power which is what's needed for hill climbing.
Also, the published 270 watt peak power of the Windsor/Salisbury is about as low as one can possibly get, even the old twist had 390 watts and the eZee bikes peak at either 500 or 576 watts according to model. Therefore those latter bikes have just half the power of those eZees.
Since you've mentioned steep hills, my strong recommendation is, try before buy.