AFAIK, most of the digitals with probes are about equal (digital thermometers aren't rock science), so many/most folks shop for price.
What I found interesting is that while you can get a thermometer-only, all the digital hygrometers I've seen were also thermometers, and the prices were the same as for thermometer-only models.
After you get your temps correct, there isn't much need for more than one unit just to keep an eye on things. Result: I have one thermometer/hygrometer in the middle of my enclosure; I know from experience that one side is 5° colder and the other side is 5° hotter, while the hygrometer measures the average humidity. I have a second thermometer at the top of the hot side, but that only functions to turn a muffin fan on & off if the hot side gets too hot.
HTH