The DHT11 has been replaced twice with similarly-priced but more accurate models, first the DHT22 and then the AHT20. In my experience, the AHT20 is a lot better than the DHT22, mainly because its power consumption is far lower, so it doesn’t mess up its readings by getting hot.

Also, at that size, I’d be very surprised if the dehumidifier has a compressor. It’s much more likely that it’s got a Peltier plate, and they’re not very good. They use a lot of power to develop and maintain a fairly small temperature difference, so if they’re in a confined space, they heat up the air quite a bit, and then the water from their tank will more easily evaporate.

If you’re willing to spend some money, a solid state ion membrane dehumidifier might be better for a small cabinet than a compressor-based one, as it’ll be easy to ensure the water goes out of the cabinet instead of into a container that can’t be emptied without opening the cabinet and letting more humidity in. They’re definitely not cheap, though. I think they’re still under patent as there’s only one manufacturer that I can find, so maybe they’re the dehumidifier of the future even if they’re not suitable right now.