ones not exactly better than the other, its just a matter of preference.
Digital delay is good in the way that all it does is create a delay effect with almost complete transparency --> no colouration of tone. And they can delay easily up to something like 16 seconds. But at the same time, digital effects can sometimes seem to steal out some of the soul and warmth of the tone.
Analogue delays tend to have a warm liquidy feeling to them, but they colour your tone slightly. A downside is your delay length tends to be pretty limited.
Downsides to both: they eat batteries like none other and tend to be really pricey.
Go a/b some in a shop. Tell me what ya think :)