I would describe the sound of all of these three 9V- pedals as solid standard without any frills and highlights.
The maximum delay times vary according to the respective version. The DDL 10 only offers 900ms, the DDL20 at least 1024ms and the DDL 1800ms.
Stereo output jacks allow to create some nice doubling effects and those who like slap back delays will also appreciate the DDL pedals.
But you will have to dispense with features like midi, and expression pedal input, modulation, true bypass and tap tempo.
Ibanez stopped producing the pedals of the DDL series a long time ago. But on the second hand market you will find all versions for very little money.
On my cult-factor-scale they all get the same value: 3 of 10 points.