Most people use the digital ones over the traditional gauges with the hands. They are said to be more accurate. I don't use any as my chameleons are housed mostly outdoors.
If you buy the ones with gauges you just as well throw your $$$ in a trash can as they are A JOKE!!! Get the ones with a probe for inside the cage or for your Cham room get a Accurite from Walmart for under $10.00 with tax and it shows current temp and humidity as well as a 24 hour high and low for both. I will post a picture in my next post. I have checked the Accurite with multiple other forms of temp monitoring including a $80.00 laser temp gun and they have all been within 1-2 degrees of each other.
I did use the digital at one time and I too did find them to be more accurate. I know some use the ones with the probe. I bought a $10 one from home depot. It was made by Accurite and seemed to do the trick!