Ultrasonic vs evaporative humidifier, which one should I choose?

The most important thing is to think about where you're going to use the humidifier because each one has its limitations. The ultrasonic disperses finer particles and heats the air less, ideal if you're looking for something compact and energy-efficient, but it leaves white dust if you have hard water. The evaporative is slower and more natural, doesn't leave residue, but needs more frequent filter maintenance and uses more energy, so if you have really hard water or want something with no upkeep, the ultrasonic works better for you; if your thing is sleeping peacefully without noise and you don't mind changing filters once in a while, the evaporative is better.

Ultrasonic humidifiers leave white dust everywhere if you have hard water, and that's a total mess that people don't really talk about. If your water's soft or you use distilled it's fine, but if not, an evaporative one will save you a ton of cleaning.

Do you have any idea how hard the water is in your area? because that's what really decides everything. If it's really chalky, the ultrasonic will get everything dirty with white dust and it's a pain to keep cleaning; the evaporative one avoids that but uses more energy and is slower.

It's not that one is better than the other in general, it really depends on your specific situation. Here at home I have an ultrasonic one and the water is pretty hard, so yeah, it does leave that white powder on the nearby furniture, but since I mainly use it in my son's room when he has a cold and I don't leave it running all day, honestly it doesn't bother me that much to clean it from time to time, and it keeps the air much more comfortable without heating it up when it's already pretty hot in summer.