Does the decreased gravity and atmosphere make it easier to create a pressure differential, or harder?
According to Wikipedia, the atmospheric pressure on Mars is about $0.6$% of the Earth's. This means that the force and work required to create vacuum on Mars should be about 167 times smaller.
It could be done, for instance, in a syringe with the sealed tip. The pressure on the back side of the plunger, open to the Mars atmosphere, will be very small, making it easy to pull the plunger and create vacuum inside the barrel.
A vacuum cleaner, in theory, would also require much less energy, but it won't do much of useful work, since it won't be able to create sufficient pressure difference to pick up dust (taking into account that the gravity on Mars is about $38$% of the gravity on Earth).