Hatsan spark, nomad or yong heng?

Spark, Nomad and Traveler are the same design. Slow and noisy but no water needed to cool them and easy to store in a drawer when not in use. If I had a clean shop to work in and to store my gear in, I would go for the YH design. I do not have a clean hobby room and I need to clean up after myself every time I use my stuff. Don't expect them to live long lives if you constantly fill SCBA tanks. The small units are not designed for long runs.
 
They are all Chinese compressors so its hard to say. I bought a Hong Heng a couple years back then overheated it badly three times cuz I did not plug the pump in. My bad! So I bought another for back up. I used the back up, when it got here, just cuz it was new and it broke within an hour or two of use. Someone at the factory did not put locktight on the second stage piston so it backed off, slammed against the head and broke. Only twelve dollars for the new part though and it was easy to find. The one I mistreated on the other hand is still werqing fine. It's the luck of the draw with much of the Chinese stuff we buy. Still I love my Yong Heng it fills fairly quickly, low maintenance and is lasting through the years. Remember also the Yong Heng is water cooled so likely will last a bit longer all things considered.

https://www.airgunnation.com/topic/a-tale-of-two-yong-hengs/
 
I've had good service from an older YH (almost certainly the weaker piston model) for over a year as well. As is well noted above, keeping it cool is critical and that is more work than some of the other compressors noted but still not too bad if you have a little space. The air gun world is certainly blessed with lots of options in the compressor area today.