Most true compressors use oil for lubrication. Oil lubricated compressors require you to change the break in oil after 5 hours or so. Booster compressors like the Shoebox, Altaros, etc. require a separate first stage feeder compressor. The $300-400 Chinese compressors omit a decent water separator tower and they require a separate bucket for cooling. When you enter the $1299 and higher range you are getting into the realm of low maintenance and plug and play. The Carette is the least expensive compressor that has all of the features that users would prefer to have. It is plug and play after you add oil and water into it's cooling system. It has a belt drive, it's extremely quiet running at low rpms, it has adjustable pressure shutoff, an hour meter, and auto moisture bleed. Hook up your tank, turn it on, and you can walk away until it shuts off at the desired fill pressure. It has features even the $4000 dive compressors charge hundreds extra to add.
Omega compressors are also plug and play. The problem with them is that they are basically motorized hand pumps. They sound like a washing machine because they are a hand pump with lots of attractive features. They require the owner to apply grease to lube the rubber o-ring seals which wear out and require rebuilds many more times than a true high pressure compressor piston design. The rubber o-rings will require a complicated, time consuming disassembly which is beyond the capability of most buyers. Watch the 30 minute Youtube disassembly video and see if it looks complicated. Omegas were state of the art a few years ago but are not a good choice when compared to more recent compressor offerings. Omegas provide the least compressor value currently based upon their high price, obsolete design, and service requirements when compared to compressors like the Carette, Air Venturi, or Daystate LC100.
If you are willing to spend $2295 or more you enter the market of true dive compressors that are air cooled, 3 or 4 stages, super durable, and only require oil and moisture filter changes on an infrequent basis. Single user airgunners will change the oil in their compressors no more than once a year and it's a 15 minute simple maintenance. Air filter changes are even easier. The more you pay usually means better build quality of the compressor.. A true dive compressor will have higher resale value and less frequent rebuilds.