Speaking of the dual compressor;
It adds weight to an awkward place on the vehicle--most are mounted in the engine bay. I'm not a fan of adding anything to the engine bay that isn't directly engine related. If it isn't mounted in the engine bay, it presents other challenges like access with the hose, running power, etc..
If you're interested in adding the air tank to the setup, that presents a mounting challenge (and weight issue) also. My portable compressor, and recovery gear, have always sat right behind the front seats, on the floor board, between the axles.
Mostly, I like the versatility of a portable compressor. I can loan it to someone with a tire issue for quick refills, use an air tool, etc., while on the trail and I don't have to be pulled up next to them in order to reach it.
While I stated earlier that if I were to do it again it would be an engine mounted unit. I must say these are very good points. Thanks for the insight.