Air tests are sometimes useful to get sort of a baseline but because of EMI, WiFi, florescent lights and who knows what else you could have affecting results in and around our homes I don't believe any tests could be considered 100% scientific.
Even coin garden testing outdoors the soil and conditions can affect our detectors differently on different days like maybe after a heavy rain.
I have tested several detectors in the past and all of them went deeper out in the field than what I got in my home using several different types of coin and jewelry targets.
Soil can and will affect all detectors...depths I reached in the great soil in Kansas with good ID's won't even come close to what I am seeing and digging in the much hotter and iron filled soil I hunt in now in Birmingham Ala.
As far as the depth on the Vaquero there is a reason this thing has the reputation it does and why people say, "Hunt with a Vaq, bring a shovel".
I can tell you I rarely got super deep in this southern soil but early on I had an experience that showed me exactly what the Vaq is all about.
Using only the standard coil in disc and not supertuned I was hunting a tot lot in a park with wood chips and no mineralization.when I got a solid, repeating signal deep in those chips.
It was way deeper than I thought at first and I kept digging deeper and deeper till my Propointer finally started to pick this target up.
I was every bit of 10-12" deep when I finally found it, didn't measure it but it was several inches deeper than my Lesche is long because I stuck that in the hole and it was buried.
Nothing else was in or near the hole, I repeatedly kept checking because I could not believe what I was seeing.
The target was a tiny pocket rivet, very small and the kind you would find on an infant's pair of jeans.
5" limit on a copper cent...don't you believe that.
A good working Vaquero under normal conditions should easily hit and surpass that in air testing with one arm tied behind its back and blind in one eye...on a battery running low on juice.
My opinion only but backed up by several in the field real world observations.