Interesting question.
I no longer carry one because I found I never used it, and it was heavy and took up too much room. When I did carry one, my portable compressor is a Craftsman with rechargeable battery -- but it's old so not the latest in technology. At 60 to 80 PSI those little compressors just take a long time to pump up a large RV tire.
My son has a Craftsman C3 battery-operated air compressor which he uses for a horse trailer parked at a barn. I've used it and it works better than mine. His is relatively small and light, plus I carry three C3 batteries and a charger with me anyway, so that would be my choice if I needed one.
For bikes, road and mountain, I use a hand pump.
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