Go big or go home
data is clipped from their sites.
Sherpa At 40 PSI, users can expect ~8.9 CFM and at 80 PSI this drops to an impressive 5.2 CFM
Extreme outback 6 CFM free flow and a whopping 2.6 CFM at 100 psi.
ARB Dual (3CFM) @ 6Bar (90PSI)
I have seen all three of these being used. I would never buy the Sherpa or the Extreme outback due to their overall size. The outback seemed to fill 35's about the same speed as the ARB. Sherpa, was way faster.
I have had a Viair for years, still going strong and fits anywhere. If I had to replace mine, it would either be another Viair or if I could get a good price, an ARB.
I have friends with power tanks. Size and having to refill them are the only reasons I don't have one. I have been on trips where someone forgot to check their power tank and I ended up filling their tires.