which consumes less electricity?

The 4 amp will use 60 watts more, 8760 hours a year, 535000 watts per year, a kilowatt current US average is 11.6 cents, $60 a year will cost $5 month more, if it does actually use a 1/2 amp more.

But motors can be a little tricky, depending on whether the use actually puts a 1/4 hp load on, and how the efficiency of the motor when not used at full load the $5 month difference may not exist.

Your best bet at this point may be to pick a motor from a distributor with better perceived customer service.

The 4 amp motors are for the larger displacement pumps. If your motor still runs the air pump can be rebuilt using an inexpensive kit and simple hand tools.

My Clearstream aerator pump and motor lasted for 20 years before needing servicing. Then I rebuilt the pump and replaced the motor bearings. The unit has always been concealed beneath tall bushes with a dog house covering it. I tossed the felt air filter when new and installed a cylindrical paper air filter used on Sears lawn equipment with an oiled foam pre-filter. I just clean and re-oil the pre-filter and blow out the paper filter with compressed air. Still using the same paper filter and replace the foam every few years.

My neighbors have theirs right out in direct sunlight with the little round cover. They go thru pumps every 3-4 years.

Electricity is not "consumed" by anything; it is converted into other forms of energy: heat, mechanical motion, etc.

If two motors are the same horsepower, they need about the same amount of electricity to run (horsepower is proportional to watts, which is proportional to volt-amps).