Having done back to back tests in the past 3 months using Gauges from ARB and Longacre and a few Copies of the ARB EZ Deflator and Staun Deflators and come copies of the Stauns I come to realize after spending all that time and over $1000 on Gauges Deflators and Inflators, The Cold hard facts when used correctly the set of 4 Stauns are only 6 seconds Quicker than the ARB EZ Deflator and the ARB is a fair bit cheaper,
Out of 13 Gauges Only One was out by 1psi and that Gauge was a Chinese Gauge that goes from 0 to 100psi But it was only out once the Gauge got below 8psi, Baring In Mind that a Gauge that reads up to 100psi has a 2% Accuracy factor between 25 and 75psi and an accuracy factor of 3% Below 25psi and above 75psi this Gauge came well below the Accuracy Limits, and is 100% accurate above 15 to 20psi,
Out of 9 ARB Gauges and Inflators and Deflators 7 of them were absolutely Bang On ZERO and 1 read 0.3psi high and the other read 0.4psi Low at below 8 psi and I put this variation down to me swapping gauges On and Off all the Time because when the tyre was reinflated all the gauges Matched, Both of these Gauges Are still as Accurate as the most expensive analog Gauges money can buy and all the Gauges were ordered on Line So I never got to pick and choose them my self, Not One of ARB's gauges was out,
I also bought 2 Copies of the EZ deflator from Ebay and One was Spot On and the other one was ONE PSI OUT, Both of these gauges came with the Needle the wrong side of the stop post just because that is how they are shipped with the easy removal of the Bezel and Glass I put the needle the right side of the post, With the one that was ONE psi out I just loosened the screws on the Dial and moved it to match the PSI and it also now reads bang on ZERO, even though they were almost a quarter of the price of the ARB EZ Deflator and they come with a 4 way Valve Key and 4 spare Valve Caps,
Out of 13 Gauges, Inflators and Deflators Only One was not up to scratch and that was one of the most expensive Gauges that I bought So it has to be returned because it leaks and does not hold the pressure, All of the ARB and the Cheap Gauges performed perfectly and All of them are as accurate as the most expensive Gauge,
As for Digital Gauges you can buy 10 of the same Gauges and only 2 or 3 will match each other, This is due to the quality of the electronic sensors used in digital gauges and even if you spend a lot of money on them there is no guarantee that you will get a good one where as most Analog Gauges use a Brass Bourdon which makes them more Accurate and stable.
As for the ARB vs Staun the ARB EZ Deflator is Miles ahead because having a Gauge on the ARB allows you to drop the pressure to any psi you want without having to reset it to another pressure, Where as the Staun Deflators are a one trick pony which only allows you to set them for one type of terrain and they loose accuracy over time due to age, Temperature dust and grit or mishandling they can and do get moved out of adjustment, It is not uncommon for people to find that none of their stauns have the same setting as someone posted on YT, Having to reset your stauns out on the trail can add up to another hour or so to your Airing down times if you have an Issue with one or two of them, So If you like using your Staun Deflators it would be a good Idea if you carried an ARB EZ Deflator as well as your Stauns as a back up not only that if the Terrain changes then having the ARB in the Glove Box will allow you to adjust your pressures to suit, Bottom line is if you prefer the Stauns then we actually need to carry both types because all of the above.
Hope that helps.