Hi David,
I am more than happy with my Viair 450P.
BTW . you can get it on Amazon for about $190
http://www.amazon.com/Viair-40043-V...TF8&qid=1409545855&sr=8-3&keywords=viair+450p
It is slightly slower than ARB but very quiet, well built.
It has automatic thermal overload protector. I am not sure if this was your question.
Also when you release the trigger when putting air , a compressor will stop till you squeeze the trigger again. It also has a pressure switch to prevent it from damage related to overpressure.
When I compared prices from your links there was not much of a difference between ARB and Viair, but for $190 Viair 450P is a really good deal.
BTW I love like your LR4 set up a lot.

I am getting ready for fuel tank and transfer case skid plates and will go probably with Asfir sump guard like Umberto did.