A necessary evil - the compressor that is. My tool of choice for sanding is the electric sander. I find battery tools to be a PIA because I always forget to charge them, or, I leave them on the charger and ruin the battery. But, for portability - you cant beat them.
I seem to have air tools for specialized applications - such as an inline sander, small die grinders and air guns. I don't know what other options there are for spraying a quality automotive paint job - other than a robust compressor.
But yeah - the cost? not for the faint of heart...after wiring, supplies, driers, hoses, connectors, oil, and maintenance.
All in all- a mix of both seems to be the best solution to respond to either large long term tasks, or for the short 10 minute job. I don't like firing up the Big Boy compressor just to remove one or two stubborn bolts with an air impact hammer - but its nice to have to get the job done. We have a small Dewalt pancake air compressor for filling tires, blowing off dust, fixing the mower, pumping bicycle tires and other small tasks when a large volume of air is not needed.
