Air
Air is so trivial that it goes often forgotten. Engine turbo-charger, snorkel, heating/cooling and, last but not least, tire pressure depend all on it.
Should I use a hand pump, a built-in unit or a mobile air compressor? Each choice has its advantages and disadvantages. Some people still use the good old hand pump. Its mechanics are simple, it is easy to use and maintain/repair. For me it was somewhat too cumbersome though. An embedded compressor is comfortable (ready at all times, well protected under the hood, does not need extra storage space), needs only low maintenance and - if you feel like - numerous external connection boxes can be attached to it so that you don't even have to open the hood when used. However, I decided for a mobile compressor in the end. The main reasons were flexibility and price. Also, maintenance is easier in case of malfunction or failure (you don't have to dismount/mount it). I willingly accepted the disadvantages in form of less comfort (storage room that could be used otherwise, power connection, time requirement etc).
