Digital thermometers use software algorithms to convert the electrical impulses from the probes into a readout. Plus or minus 3-4F is what Maverick considers accurate. My chamber probes are right on while my food probes read 2 degrees low. I'm basically at sea level.
Additionally, the programming in digital thermometers will average the readout over time. Therms from different manufacturers will use different software. The Maverick has a rather short averaging period. My BBQ Guru has a longer averaging period. The chamber probes will read quite differently for a while but eventually the two match up. Not so with the food probes. The Guru food probe tested at 212F but reads 5 degrees hotter than the Maverick when stuck in the same piece of meat right next to each other.
For consistent results pick one make of thermometer and cook/smoke "to" it. I learned with the Maverick so that's what I go by. If I had to use the Guru exclusively it would take a little while to adapt my timings and final temps, but not long. If I had to use the lid thermometer exclusively it would take longer still to develop the "feel" for doneness since it gives the temp at the lid, not the grates, which in the
WSM will have different temps than the lid.
Talk about OCD! I'm quite analytical about mine.