I've never used a Sprint Jet. The Whispers were used quite extensively in airbrush studios. I remember in 1984 seeing whole banks of Whispers at Jostens. Jostens was the company the people that make, or made, the high school year books and, I think, class rings too. All the Whispers were operational and I didn't see any defective ones laying off to the side. That told me that the Whispers were reliable. But the workers still cooed like a loving pigeon whenever the name Silentaire (compressors) came up. They liked their Whispers but loved Silentaire because of how quiet it was.
Whisper is a oil-less piston compressor with lots of noise dampening material. It also is housed in a sealed box with holes for operating. They are built well. The motor is very heavy duty. If I had a pick with it then it would have been my wish that the air tank was .5 gallon bigger. I know the motor would handle a bigger tank.
All in all the Whispers are a quiet, work horse, compressor. Those Whispers selling at Ebay are a bargain.