Desiccant vs Compressor
Compressor humidifiers work best at higher temperatures and humidities. They are rated at a temperature of 30°C and a relative humidity of 80%.
Desiccant humidifiers work better at the lower temperatures, this for example would suit the conditions found in UK boatyards during the winter. In fact, if the temperature drops too low then parts of a compressor dehumidifier will ice up, a problem desiccant humidifiers do not have. Different compressor models have different ways of dealing with this: they either switch off, or they can have a reverse hot gas cycle which quickly heats up the frozen evaporator plates and melts the ice.
Compressor dehumidifiers do warm up the air slightly but desiccant models greatly warm it. This is obviously advantageous in a situation such as in a boat in winter helping reduce the chill and the likelihood of parts freezing up. The downside is that they use more energy.