I currently have a portable Viair 400P. It's rated as 'up to 35" tires'; 2.54 cfm (@0 psi, 1.7@50). Although not rated as 100% duty cycle, I regularly air up all my tires without stopping. Heck, leaving Pismo I also did 2 of Antonio's when his CO2 tank ran empty.
I am looking to not have to carry the compressor in the back - one less thing to dig out of storage - and just mount it under the hood. I could just hard mount the 400P, but I'd also like mo speed while I'm at it.
I won't be using it to run the truck's suspension or air tools, etc, just tires. I don't want to go to CO2 for exactly the reason I just saw with Antonio - it's super fast but if you forget to refill it you're SOL. I also don't plan to mount a tank, just doing tires I don't see much benefit as I don't plan to have the compressor on all the time, just when I'm actually using it. Though with a fixed mount unit I could always do that later if I wanted.
The ARB twin compressor is rated at 6.16 cfm@0 psi, so over twice the volume of the 400P. It's also rated continuous duty so it should run cooler/live longer than the 400P. Yes it's expensive and no I don't really need it, but again, who doesn't want mo' speed?
Looking at the Viair website, I see they have the 400C dual-pack listing 4.55 cfm@0 psi / 3.25 cfm@50 psi. It is rated 33% duty cycle though. I see Walmart has this for $288, so maybe I should look into this more. The 400C dual-pack looks like their highest volume offering. It might need a little more space to mount given the way it's made.
BTW, the Viair site is stupid-slow tonight.