Is the application of a desiccant drier better than a refrigeration drier?

Certainly not at ambient temperatures above 25 °C / 77 F. The compressed air from the air compressor normally has a temperature that is 10 to 15 °C above ambient temperature. Correct-sized refrigeration drier not only guarantees a sufficient dew point of the feed air to the gas generator but will also cool the feed air. Feed air cooling has two important beneficial effects:

Your nitrogen or oxygen generator will have a higher gas production at a better efficiency.

The molecular sieve of your nitrogen or oxygen generator will not be exposed to too high operational temperatures and thus ensuring a longer lifetime of the same.