Which of these temp/humidity readers would you trust more?

[Lion]

To be completely honest, neither are very reliable.

The big question on the dial type is if it has a cardboard baking or metal. The cardboard backed dials start to read further and further off as the cardboard swells due to the moisture. Metal backed dials are much better, and usually have the ability to be calibrated (using the salt test to calibrate it)

Electronic sensors have a similar issue. The older they are the less reliable they get. Even still 5% off each other is actually very good. Both devices probably have +/- 5% or even +/- 10% error built into them.

Accurate thermometers and hygrometers are very expensive, hundreds to thousands of dollars. This means that most people in the reptile hobby aren't going to be able to afford them. What people need to find are precise (see precision vs accuracy below) thermometers and hygrometers that can be relied upon to give consistent readings. Even if they are incorrect. That way you can over time learn how far off the readings are and compensate for them.

AWESOME info, thank you!

Here's how the fancy infrared temp guns work...The infrared gun detects the heat signature of an object with optic sensors. These sensors are a series of lenses and mirrors that condense the infrared energy that an object omits onto a detector that transforms the infrared energy into an electrical signal. This signal is interpreted and turned into a temperature reading on the gun's display.

I know that my dad has a temp gun (the guy spent twenty years building houses, and now works as a home inspector for houses on the market, so he's got ALL the goods), so this should be really helpful as well. ;D