If you are leaning towards ARB but won't need to use it very often, I can tell you my ARB CKMA 12 fit snugly into a seemingly unusable space, and has worked very well. It is one of the single compressor models, and can air up my tires (~32"s) from 20# to 40# in about 2 mins each. The installation instructions were easy to understand, and came with the complete wiring harness, a rocker switch (I opted for a push button that fit in one of my dashboard blank slots), and the quick connect for an air hose. There are two set screws in the aluminum body that can be removed to install solenoids for air lockers or to run a hose for a reservoir tank. The body can rotate, as can the hose connection, so you can align it to work with wherever you mount it. Mine is mounted in a small space behind the passenger headlight. I've had mine for about 2.5 years with no issues.
It isn't great for blowing off dirt/dust without a reservoir tank as you are only seeing the compressor output (no stored energy), and the double compressor model will be faster and can run pneumatic tools, but for tires and air mattresses this one works just fine. Also, no maintenance required. Once on, it will sense what the discharge pressure is and shut itself down until you start using air or enough leaks out, then will kick on again.
Got my father one for his birthday, and he absolutely loves it. No more trips to the gas station for air.
