Here's a link to a tire pressure gauge test Motorhome Magazine did.
http://www.motorhome.com/rv-how-to/rv-tech-tips/testing-tire-gauges/Note that while their original intent wasn't to pick a winner they did feel that the Milton S-976 was far and away the best of the bunch. It was dead on for every pressure they tested.
While they do cost a little more, they are rugged and seem to last for ever. I have a couple Milton gauges left over from my days as a garage owner. They are now 40+ years old and still accurate